drm/xe: Remove unused xe_sync_entry_wait

xe_sync_entry_wait is no longer used, remove it.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240717140429.1396820-2-matthew.brost@intel.com