drm/amdgpu: add UAPI for allocating doorbell memory

This patch adds flags for a new gem domain AMDGPU_GEM_DOMAIN_DOORBELL
in the UAPI layer.

V2: Drop 'memory' from description (Christian)

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Reviewed-by: Christian Koenig <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>

include/uapi/drm/amdgpu_drm.h

@@ -94,6 +94,9 @@ extern "C" {
  *
  * %AMDGPU_GEM_DOMAIN_OA	Ordered append, used by 3D or Compute engines
  * for appending data.
+ *
+ * %AMDGPU_GEM_DOMAIN_DOORBELL	Doorbell. It is an MMIO region for
+ * signalling user mode queues.
  */
 #define AMDGPU_GEM_DOMAIN_CPU		0x1
 #define AMDGPU_GEM_DOMAIN_GTT		0x2
@@ -101,12 +104,14 @@ extern "C" {
 #define AMDGPU_GEM_DOMAIN_GDS		0x8
 #define AMDGPU_GEM_DOMAIN_GWS		0x10
 #define AMDGPU_GEM_DOMAIN_OA		0x20
+#define AMDGPU_GEM_DOMAIN_DOORBELL	0x40
 #define AMDGPU_GEM_DOMAIN_MASK		(AMDGPU_GEM_DOMAIN_CPU | \
 					 AMDGPU_GEM_DOMAIN_GTT | \
 					 AMDGPU_GEM_DOMAIN_VRAM | \
 					 AMDGPU_GEM_DOMAIN_GDS | \
 					 AMDGPU_GEM_DOMAIN_GWS | \
-					 AMDGPU_GEM_DOMAIN_OA)
+					 AMDGPU_GEM_DOMAIN_OA | \
+					 AMDGPU_GEM_DOMAIN_DOORBELL)
 
 /* Flag that CPU access will be required for the case of VRAM domain */
 #define AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED	(1 << 0)