drm/xe: Use xe_bo_lock()/xe_bo_unlock() helpers

There is no change in functionality. Using the helper function
defined within the driver for locking/unlocking the reservation
object.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240424043910.2190376-3-himal.prasad.ghimiray@intel.com