drm/xe/tests: Grab a memory access reference around the migrate sanity test

It appears we don't hold a memory access reference for the accesses in
this test, which may results in printed warnings and possibly the GT
not woken up for the memory accesses.

Add a memory access reference around the test.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/tests/xe_migrate.c

@@ -366,7 +366,9 @@ static int migrate_test_run_device(struct xe_device *xe)
 
 		kunit_info(test, "Testing gt id %d.\n", id);
 		xe_vm_lock(m->eng->vm, &ww, 0, true);
+		xe_device_mem_access_get(xe);
 		xe_migrate_sanity_test(m, test);
+		xe_device_mem_access_put(xe);
 		xe_vm_unlock(m->eng->vm, &ww);
 	}