netfilter: ctnetlink: fix gcc warning during compilation

This patch fixes a (bogus?) gcc warning during compilation:

net/netfilter/nf_conntrack_netlink.c:1234: warning: 'helpname' may be used uninitialized in this function
net/netfilter/nf_conntrack_netlink.c:991: warning: 'helpname' may be used uninitialized in this function

In fact, helpname is initialized by ctnetlink_parse_help() so
I cannot see a way to use it without being initialized.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_netlink.c

@@ -988,7 +988,7 @@ ctnetlink_change_helper(struct nf_conn *ct, struct nlattr *cda[])
 {
 	struct nf_conntrack_helper *helper;
 	struct nf_conn_help *help = nfct_help(ct);
-	char *helpname;
+	char *helpname = NULL;
 	int err;
 
 	/* don't change helper of sibling connections */
@@ -1231,7 +1231,7 @@ ctnetlink_create_conntrack(struct nlattr *cda[],
 
 	rcu_read_lock();
  	if (cda[CTA_HELP]) {
- 		char *helpname;
+		char *helpname = NULL;
  
  		err = ctnetlink_parse_help(cda[CTA_HELP], &helpname);
  		if (err < 0)