Unlock reservations in the error code path of virtio_gpu_object_create()
to silence debug warning splat produced by ww_mutex_destroy(&obj->lock)
when GEM is released with the held lock.

Cc: stable@vger.kernel.org
Fixes: 30172efb ("drm/virtio: blob prep: refactor getting pages and attaching backing")
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220630200726.1884320-4-dmitry.osipenko@collabora.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>