virtio: Add missing documentation for structure fields

Add missing documentation for the vqs_list_lock field of struct virtio_device,
and the validate field of struct virtio_driver.

./scripts/kernel-doc says:

 .../virtio.h:131: warning: Function parameter or member 'vqs_list_lock' not described in 'virtio_device'
 .../virtio.h:192: warning: Function parameter or member 'validate' not described in 'virtio_driver'
 2 warnings as Errors

No functional changes intended.
Signed-off-by: Simon Horman <horms@kernel.org>
Message-Id: <20230510-virtio-kdoc-v3-1-e2681ed7a425@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

include/linux/virtio.h

@@ -103,6 +103,7 @@ int virtqueue_resize(struct virtqueue *vq, u32 num,
  * @config_enabled: configuration change reporting enabled
  * @config_change_pending: configuration change reported while disabled
  * @config_lock: protects configuration change reporting
+ * @vqs_list_lock: protects @vqs.
  * @dev: underlying device.
  * @id: the device type identification (used to match it with a driver).
  * @config: the configuration ops for this device.
@@ -117,7 +118,7 @@ struct virtio_device {
 	bool config_enabled;
 	bool config_change_pending;
 	spinlock_t config_lock;
-	spinlock_t vqs_list_lock; /* Protects VQs list access */
+	spinlock_t vqs_list_lock;
 	struct device dev;
 	struct virtio_device_id id;
 	const struct virtio_config_ops *config;
@@ -160,6 +161,8 @@ size_t virtio_max_dma_size(const struct virtio_device *vdev);
  * @feature_table_size: number of entries in the feature table array.
  * @feature_table_legacy: same as feature_table but when working in legacy mode.
  * @feature_table_size_legacy: number of entries in feature table legacy array.
+ * @validate: the function to call to validate features and config space.
+ *            Returns 0 or -errno.
  * @probe: the function to call when a device is found.  Returns 0 or -errno.
  * @scan: optional function to call after successful probe; intended
  *    for virtio-scsi to invoke a scan.