drm/msm: fix BUG_ON() in error cleanup path

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
index 4a08655..a9579ce 100644
--- a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
+++ b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
@@ -147,7 +147,7 @@
 	if (mdp4_kms->blank_cursor_iova)
 		msm_gem_put_iova(mdp4_kms->blank_cursor_bo, mdp4_kms->id);
 	if (mdp4_kms->blank_cursor_bo)
-		drm_gem_object_unreference(mdp4_kms->blank_cursor_bo);
+		drm_gem_object_unreference_unlocked(mdp4_kms->blank_cursor_bo);
 	kfree(mdp4_kms);
 }