drm/ast: Use lockless gem BO free callback

No dev->struct_mutex anywhere to be seen.

Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464630800-30786-3-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/ast/ast_drv.c

@@ -209,7 +209,7 @@ static struct drm_driver driver = {
 	.minor = DRIVER_MINOR,
 	.patchlevel = DRIVER_PATCHLEVEL,
 
-	.gem_free_object = ast_gem_free_object,
+	.gem_free_object_unlocked = ast_gem_free_object,
 	.dumb_create = ast_dumb_create,
 	.dumb_map_offset = ast_dumb_mmap_offset,
 	.dumb_destroy = drm_gem_dumb_destroy,