drm/virtio: fix the missed drm_gem_object_put() in virtio_gpu_user_framebuffer_create()

virtio_gpu_user_framebuffer_create() misses to call drm_gem_object_put()
in an error path. Add the missed function call to fix it.
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1633770560-11658-1-git-send-email-jingxiangfeng@huawei.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -308,8 +308,10 @@ virtio_gpu_user_framebuffer_create(struct drm_device *dev,
 		return ERR_PTR(-EINVAL);
 
 	virtio_gpu_fb = kzalloc(sizeof(*virtio_gpu_fb), GFP_KERNEL);
-	if (virtio_gpu_fb == NULL)
+	if (virtio_gpu_fb == NULL) {
+		drm_gem_object_put(obj);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	ret = virtio_gpu_framebuffer_init(dev, virtio_gpu_fb, mode_cmd, obj);
 	if (ret) {