drm/qxl: qxl_release leak in qxl_hw_surface_alloc()

Cc: stable@vger.kernel.org
Fixes: 8002db63

 ("qxl: convert qxl driver to proper use for reservations")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Link: http://patchwork.freedesktop.org/patch/msgid/2e5a13ae-9ab2-5401-aa4d-03d5f5593423@virtuozzo.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>