drm/xe: Wrappers for setting and getting LRC references

drm/xe: Wrappers for setting and getting LRC references

There is a small but non-zero chance that VF post migration fixups
are running on an exec queue during teardown. The chances are
decreased by starting the teardown by releasing guc_id, but remain
non-zero. On the other hand the sync between fixups and EQ creation
(wait_valid_ggtt) drastically increases the chance for such parallel
teardown if queue creation error path is entered (err_lrc label).

The exec queue itself is not going to cause an issue, but LRCs have
a small chance of getting freed during the fixups.

Creating a setter and a getter makes it easier to protect the fixup
operations with a lock. For other driver activities, the original
access method (without any protection) can still be used.

v2: Separate lock, only for LRCs. Kerneldoc fixes. Subject tag fix.

Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patch.msgid.link/20260226212701.2937065-3-tomasz.lis@intel.com