drm/nouveau: uapi: fix kerneldoc warnings

As of commit b77fdd6a ("scripts/kernel-doc: restore warning for
Excess struct/union"), we see the following warnings when running 'make
htmldocs':

  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_OP_MAP' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_OP_UNMAP' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_SPARSE' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:336: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_RUN_ASYNC' description in 'drm_nouveau_vm_bind'

The problem is that these values are #define constants, but had kerneldoc
comments attached to them as if they were actual struct members.

There are a number of ways we could fix this, but I chose to draw
inspiration from include/uapi/drm/i915_drm.h, which pulls them into the
corresponding kerneldoc comment for the struct member that they are
intended to be used with.

To keep the diff readable, there are a number of things I _didn't_ do in
this patch, but which we should also consider:

- This is pretty good documentation, but it ends up in gpu/driver-uapi,
  which is part of subsystem-apis/ when it really ought to display under
  userspace-api/ (the "Linux kernel user-space API guide" book of the
  documentation).

- More generally, we might want a warning if include/uapi/ files are
  kerneldoc'd outside userspace-api/.

- I'd consider it cleaner if the #defines appeared between the kerneldoc
  for the member and the member itself (which is something other DRM-
  related UAPI docs do).

- The %IDENTIFIER kerneldoc syntax is intended for "constants", and is
  more appropriate in this context than ``IDENTIFIER`` or &IDENTIFIER.
  The DRM docs aren't very consistent on this.

Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231225065145.3060754-1-vegard.nossum@oracle.com

include/uapi/drm/nouveau_drm.h

@@ -238,34 +238,32 @@ struct drm_nouveau_vm_init {
 struct drm_nouveau_vm_bind_op {
 	/**
 	 * @op: the operation type
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_OP_MAP - Map a GEM object to the GPU's VA
+	 * space. Optionally, the &DRM_NOUVEAU_VM_BIND_SPARSE flag can be
+	 * passed to instruct the kernel to create sparse mappings for the
+	 * given range.
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_OP_UNMAP - Unmap an existing mapping in the
+	 * GPU's VA space. If the region the mapping is located in is a
+	 * sparse region, new sparse mappings are created where the unmapped
+	 * (memory backed) mapping was mapped previously. To remove a sparse
+	 * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
 	 */
 	__u32 op;
-/**
- * @DRM_NOUVEAU_VM_BIND_OP_MAP:
- *
- * Map a GEM object to the GPU's VA space. Optionally, the
- * &DRM_NOUVEAU_VM_BIND_SPARSE flag can be passed to instruct the kernel to
- * create sparse mappings for the given range.
- */
 #define DRM_NOUVEAU_VM_BIND_OP_MAP 0x0
-/**
- * @DRM_NOUVEAU_VM_BIND_OP_UNMAP:
- *
- * Unmap an existing mapping in the GPU's VA space. If the region the mapping
- * is located in is a sparse region, new sparse mappings are created where the
- * unmapped (memory backed) mapping was mapped previously. To remove a sparse
- * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
- */
 #define DRM_NOUVEAU_VM_BIND_OP_UNMAP 0x1
 	/**
 	 * @flags: the flags for a &drm_nouveau_vm_bind_op
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_SPARSE - Indicates that an allocated VA
+	 * space region should be sparse.
 	 */
 	__u32 flags;
-/**
- * @DRM_NOUVEAU_VM_BIND_SPARSE:
- *
- * Indicates that an allocated VA space region should be sparse.
- */
 #define DRM_NOUVEAU_VM_BIND_SPARSE (1 << 8)
 	/**
 	 * @handle: the handle of the DRM GEM object to map
@@ -301,17 +299,17 @@ struct drm_nouveau_vm_bind {
 	__u32 op_count;
 	/**
 	 * @flags: the flags for a &drm_nouveau_vm_bind ioctl
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_RUN_ASYNC - Indicates that the given VM_BIND
+	 * operation should be executed asynchronously by the kernel.
+	 *
+	 * If this flag is not supplied the kernel executes the associated
+	 * operations synchronously and doesn't accept any &drm_nouveau_sync
+	 * objects.
 	 */
 	__u32 flags;
-/**
- * @DRM_NOUVEAU_VM_BIND_RUN_ASYNC:
- *
- * Indicates that the given VM_BIND operation should be executed asynchronously
- * by the kernel.
- *
- * If this flag is not supplied the kernel executes the associated operations
- * synchronously and doesn't accept any &drm_nouveau_sync objects.
- */
 #define DRM_NOUVEAU_VM_BIND_RUN_ASYNC 0x1
 	/**
 	 * @wait_count: the number of wait &drm_nouveau_syncs