drm/i915: Don't reuse commit_work for the cleanup

drm/i915: Don't reuse commit_work for the cleanup

Currently we reuse the commit_work for a later cleanup step.
Let's not do that so that atomic ioctl handler won't accidentally
wait for the cleanup work when it really wants to just wait on the
commit_tail() part. We'll just add another work struct for the
cleanup.

Cc: Brian Geffon <bgeffon@google.com>
Cc: Vidya Srinivas <vidya.srinivas@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241127061117.25622-2-ville.syrjala@linux.intel.com
Reviewed-by: Vidya Srinivas <vidya.srinivas@intel.com>
Tested-by: Vidya Srinivas <vidya.srinivas@intel.com>