drm/virtgpu api: cross-device feature

This feature was recently added to virtio-gpu, lets make
it userspace queryable. It's an error to use
BLOB_FLAG_USE_CROSS_DEVICE when this feature is not present.

Signed-off-by: Gurchetan Singh <[e-mail]>
Acked-by: Tomeu Vizoso <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Gerd Hoffmann <[e-mail]>

include/uapi/drm/virtgpu_drm.h

···
 #define VIRTGPU_PARAM_CAPSET_QUERY_FIX 2 /* do we have the capset fix */
 #define VIRTGPU_PARAM_RESOURCE_BLOB 3 /* DRM_VIRTGPU_RESOURCE_CREATE_BLOB */
 #define VIRTGPU_PARAM_HOST_VISIBLE 4 /* Host blob resources are mappable */
+#define VIRTGPU_PARAM_CROSS_DEVICE 5 /* Cross virtio-device resource sharing  */
 
 struct drm_virtgpu_getparam {
 	__u64 param;