net/ipv4: avoid compile error in fib_info_nh_uses_dev

net/ipv4/fib_frontend.c: In function 'fib_info_nh_uses_dev':
net/ipv4/fib_frontend.c:322:6: error: unused variable 'ret' [-Werror=unused-variable]
cc1: all warnings being treated as errors

Fixes: 78f2756c5fc0 ("net/ipv4: Move device validation to helper")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Ahern <dsahern@gmail.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_frontend.c

@@ -318,9 +318,9 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
 bool fib_info_nh_uses_dev(struct fib_info *fi, const struct net_device *dev)
 {
 	bool dev_match = false;
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
 	int ret;
 
-#ifdef CONFIG_IP_ROUTE_MULTIPATH
 	for (ret = 0; ret < fi->fib_nhs; ret++) {
 		struct fib_nh *nh = &fi->fib_nh[ret];