caif: Fix missing msg_namelen update in caif_seqpkt_recvmsg()

The current code does not fill the msg_name member in case it is set.
It also does not set the msg_namelen member to 0 and therefore makes
net/socket.c leak the local, uninitialized sockaddr_storage variable
to userland -- 128 bytes of kernel stack memory.

Fix that by simply setting msg_namelen to 0 as obviously nobody cared
about caif_seqpkt_recvmsg() not filling the msg_name in case it was
set.

Cc: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static void caif_flow_ctrl(struct sock *sk, int mode)
{
	struct caifsock *cf_sk;
	cf_sk = container_of(sk, struct caifsock, sk);
	if (cf_sk->layer.dn && cf_sk->layer.dn->modemcmd)
		cf_sk->layer.dn->modemcmd(cf_sk->layer.dn, mode);
}

static void caif_flow_ctrl(struct sock *sk, int mode)
{
	struct caifsock *cf_sk;
	cf_sk = container_of(sk, struct caifsock, sk);
	if (cf_sk->layer.dn && cf_sk->layer.dn->modemcmd)
		cf_sk->layer.dn->modemcmd(cf_sk->layer.dn, mode);
}
