mISDN: Fix a sleep-in-atomic bug

The driver may sleep under a read spin lock, and the function call path is:
send_socklist (acquire the lock by read_lock)
  skb_copy(GFP_KERNEL) --> may sleep

To fix it, the "GFP_KERNEL" is replaced with "GFP_ATOMIC".
Signed-off-by: NJia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/isdn/mISDN/stack.c

@@ -75,7 +75,7 @@ send_socklist(struct mISDN_sock_list *sl, struct sk_buff *skb)
 		if (sk->sk_state != MISDN_BOUND)
 			continue;
 		if (!cskb)
-			cskb = skb_copy(skb, GFP_KERNEL);
+			cskb = skb_copy(skb, GFP_ATOMIC);
 		if (!cskb) {
 			printk(KERN_WARNING "%s no skb\n", __func__);
 			break;