drm/xe: Create a helper function to init job's user fence

drm/xe: Create a helper function to init job's user fence

Refactor xe_sync_entry_signal so it doesn't have to
modify xe_sched_job struct instead create a new helper function
to set user fence values for a job.

v2: Move the sync type check to xe_sched_job_init_user_fence(Lucas)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240321161142.4954-1-nirmoy.das@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>