net/xfrm_user: Use in_compat_syscall to deny compat syscalls

The code wants to prevent compat code from receiving messages.  Use
in_compat_syscall for this.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

net/xfrm/xfrm_user.c

@@ -2449,7 +2449,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 	int type, err;
 
 #ifdef CONFIG_COMPAT
-	if (is_compat_task())
+	if (in_compat_syscall())
 		return -ENOTSUPP;
 #endif