drm/amdkfd: Fix NULL pointer dereference in svm_migrate_to_ram()

./drivers/gpu/drm/amd/amdkfd/kfd_migrate.c:985:58-62: ERROR: p is NULL but dereferenced.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2549
Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Yang Li <[e-mail]>
Reviewed-by: Felix Kuehling <[e-mail]>
Signed-off-by: Felix Kuehling <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdkfd/kfd_migrate.c

···
 out_unlock_svms:
 	mutex_unlock(&p->svms.lock);
 out_unref_process:
+	pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
 	kfd_unref_process(p);
 out_mmput:
 	mmput(mm);
-
-	pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
-
 	return r ? VM_FAULT_SIGBUS : 0;
 }