drm/xe: Move page reclaim done_handler to own func

drm/xe: Move page reclaim done_handler to own func

Originally, page reclamation is handled by the same fence as tlb
invalidation and uses its seqno, so there was no reason to separate out
the handlers. However in hindsight, for readability, and possible
future changes, it seems more beneficial to move this all out to its own
function.

Signed-off-by: Brian Nguyen <brian3.nguyen@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Shuicheng Lin <shuicheng.lin@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://patch.msgid.link/20260305171546.67691-7-brian3.nguyen@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>