drm/prime: fix error path in drm_gem_prime_fd_to_handle

handle_unreference only clears up the obj->name and the reference,
but would leave a dangling handle in the idr. The right thing
to do is to call handle_delete.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_prime.c

@@ -476,7 +476,7 @@ fail:
 	/* hmm, if driver attached, we are relying on the free-object path
 	 * to detach.. which seems ok..
 	 */
-	drm_gem_object_handle_unreference_unlocked(obj);
+	drm_gem_handle_delete(file_priv, *handle);
 out_put:
 	dma_buf_put(dma_buf);
 	mutex_unlock(&file_priv->prime.lock);