ISDN, Gigaset: Fix memory leak in do_disconnect_req()

Hi,

In drivers/isdn/gigaset/capi.c::do_disconnect_req() we will leak the
memory allocated (with kmalloc) to 'b3cmsg' if the call to alloc_skb()
fails.

...
		b3cmsg = kmalloc(sizeof(*b3cmsg), GFP_KERNEL);
	allocation here ------^
		if (!b3cmsg) {
			dev_err(cs->dev, "%s: out of memory\n", __func__);
			send_conf(iif, ap, skb, CAPI_MSGOSRESOURCEERR);
			return;
		}
		capi_cmsg_header(b3cmsg, ap->id, CAPI_DISCONNECT_B3, CAPI_IND,
				 ap->nextMessageNumber++,
				 cmsg->adr.adrPLCI | (1 << 16));
		b3cmsg->Reason_B3 = CapiProtocolErrorLayer1;
		b3skb = alloc_skb(CAPI_DISCONNECT_B3_IND_BASELEN, GFP_KERNEL);
		if (b3skb == NULL) {
			dev_err(cs->dev, "%s: out of memory\n", __func__);
			send_conf(iif, ap, skb, CAPI_MSGOSRESOURCEERR);
			return;
	leak here ------^
...

This leak is easily fixed by just kfree()'ing the memory allocated to
'b3cmsg' right before we return. The following patch does that.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>