drm/xe/selftests: restart GT after xe_bo_restore_kernel()

Test seems to be failing badly after calling xe_bo_restore_kernel().
Taking a snapshot of the CTB and copying back a potentially old version
seems risky, depending on what might have been inflight. Also it seems
snapshotting the ADS object and copying back results in serious
breakage. Normally when calling xe_bo_restore_kernel() we always fully
restart the GT, which re-intializes such things.  We could potentially
skip saving and restoring such objects in xe_bo_evict_all() however
seems quite fragile not to also restart the GT. Try to do that here by
triggering a GT reset.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>