xen/pvcalls: use GFP_ATOMIC under spin lock

A spin lock is taken here so we should use GFP_ATOMIC.

Fixes: 9774c6cca2 ("xen/pvcalls: implement accept command")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/pvcalls-front.c

@@ -805,7 +805,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 		pvcalls_exit();
 		return ret;
 	}
-	map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
+	map2 = kzalloc(sizeof(*map2), GFP_ATOMIC);
 	if (map2 == NULL) {
 		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 			  (void *)&map->passive.flags);