drm/vc4: Use lockless gem BO free callback

No dev->struct_mutex anywhere to be seen.

Cc: Eric Anholt <eric@anholt.net>
Reviewed-by: NEric Anholt <eric@anholt.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464630800-30786-16-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/vc4/vc4_drv.c

@@ -99,7 +99,7 @@ static struct drm_driver vc4_drm_driver = {
 #endif
 
 	.gem_create_object = vc4_create_object,
-	.gem_free_object = vc4_free_object,
+	.gem_free_object_unlocked = vc4_free_object,
 	.gem_vm_ops = &drm_gem_cma_vm_ops,
 
 	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,