drm/radeon: properly document reloc priority mask

Instead of hard coding the value properly document
that this is an userspace interface.

No intended functional change.
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_cs.c

@@ -132,7 +132,8 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 		 * the buffers used for read only, which doubles the range
 		 * to 0 to 31. 32 is reserved for the kernel driver.
 		 */
-		priority = (r->flags & 0xf) * 2 + !!r->write_domain;
+		priority = (r->flags & RADEON_RELOC_PRIO_MASK) * 2
+			   + !!r->write_domain;
 
 		/* the first reloc of an UVD job is the msg and that must be in
 		   VRAM, also but everything into VRAM on AGP cards to avoid

include/uapi/drm/radeon_drm.h

@@ -944,6 +944,7 @@ struct drm_radeon_cs_chunk {
 };
 
 /* drm_radeon_cs_reloc.flags */
+#define RADEON_RELOC_PRIO_MASK		(0xf << 0)
 
 struct drm_radeon_cs_reloc {
 	uint32_t		handle;