netrom: fix invalid use of sizeof in nr_recvmsg()

sizeof() when applied to a pointer typed expression gives the size of the
pointer, not that of the pointed data.
Introduced by commit 3ce5ef(netrom: fix info leak via msg_name in nr_recvmsg)
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netrom/af_netrom.c

@@ -1173,7 +1173,7 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
 	}
 
 	if (sax != NULL) {
-		memset(sax, 0, sizeof(sax));
+		memset(sax, 0, sizeof(*sax));
 		sax->sax25_family = AF_NETROM;
 		skb_copy_from_linear_data_offset(skb, 7, sax->sax25_call.ax25_call,
 			      AX25_ADDR_LEN);