drm/xe/ct: drop irq usage of xa_erase()

Unclear why disabling interrupts is needed here. Nothing seems to be
touching fence_lookup and its corresponding lock from an irq so there
should be no risk of deadlock.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241001084346.98516-8-matthew.auld@intel.com