ipvs: fix warning on unused variable

When CONFIG_IP_VS_IPV6 is not defined, build produced this warning:

net/netfilter/ipvs/ip_vs_ctl.c:899:6: warning: unused variable ‘ret’ [-Wunused-variable]
  int ret = 0;
      ^~~

Fix this by moving the declaration of 'ret' in the CONFIG_IP_VS_IPV6
section in the same function.

While at it, drop its unneeded initialisation.

Fixes: 098e13f5 ("ipvs: fix dependency on nf_defrag_ipv6")
Reported-by: NStefano Brivio <sbrivio@redhat.com>
Signed-off-by: NAndrea Claudi <aclaudi@redhat.com>
Reviewed-by: NStefano Brivio <sbrivio@redhat.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/ipvs/ip_vs_ctl.c

@@ -896,12 +896,13 @@ ip_vs_new_dest(struct ip_vs_service *svc, struct ip_vs_dest_user_kern *udest,
 {
 	struct ip_vs_dest *dest;
 	unsigned int atype, i;
-	int ret = 0;
 
 	EnterFunction(2);
 
 #ifdef CONFIG_IP_VS_IPV6
 	if (udest->af == AF_INET6) {
+		int ret;
+
 		atype = ipv6_addr_type(&udest->addr.in6);
 		if ((!(atype & IPV6_ADDR_UNICAST) ||
 			atype & IPV6_ADDR_LINKLOCAL) &&