i965: Fix memory leaks in brw_upload_cs_work_groups_surface().

i965: Fix memory leaks in brw_upload_cs_work_groups_surface().

This was taking a reference to the 64kB upload buffer and never
returning it, leaking a reference each time this atom triggered.

This leaked lots of 64kB upload BOs, eventually running us out of
of VMA space.  This would usually happen when using mpv to watch a
movie, after 20-40 minutes.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110134
Fixes: 63d7b33f516 i965/cs: Setup surface binding for gl_NumWorkGroups
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>