drm/xe/xe_exec : In xe_exec_ioctl remove deadcode

drm/xe/xe_exec : In xe_exec_ioctl remove deadcode

At label err_unlock_list the condition write_label will never be true.
Remove the deadcode line for write_label true.

Reported by static analyzer.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Tejas Upadhyay <tejas.upadhyay@intel.com>
Cc: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240313150545.2830408-3-himal.prasad.ghimiray@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>