drm/qxl: reorder calls in qxl_device_fini().

Reorder calls in qxl_device_fini().  Cleaning up gem & ttm
might trigger qxl commands, so we should do that before
releaseing command rings.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20200210113753.5614-2-kraxel@redhat.com