drm/radeon: Add the missed drm_gem_object_put() in radeon_user_framebuffer_create()

radeon_user_framebuffer_create() misses to call drm_gem_object_put() in
an error path. Add the missed function call to fix it.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_display.c

@@ -1325,6 +1325,7 @@ radeon_user_framebuffer_create(struct drm_device *dev,
 	/* Handle is imported dma-buf, so cannot be migrated to VRAM for scanout */
 	if (obj->import_attach) {
 		DRM_DEBUG_KMS("Cannot create framebuffer from imported dma_buf\n");
+		drm_gem_object_put(obj);
 		return ERR_PTR(-EINVAL);
 	}