gallium/u_threaded: fix buffer busyness tracking

gallium/u_threaded: fix buffer busyness tracking

The order of calls was incorrect.

Fixes: e9c41b321488c23b - gallium/u_threaded: add buffer lists - tracking of buffers referenced by tc
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5327

Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-By: Jonathan Strobl <jonathan.strobl@gmx.de>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16989>