ipv4: Remove unused but set variable

Remove the unused but set variable dev in ip_do_fragment to fix the
following GCC warning when building with 'W=1':

  net/ipv4/ip_output.c: In function ‘ip_do_fragment’:
  net/ipv4/ip_output.c:541:21: warning: variable ‘dev’ set but not used [-Wunused-but-set-variable]
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_output.c

@@ -538,7 +538,6 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 {
 	struct iphdr *iph;
 	int ptr;
-	struct net_device *dev;
 	struct sk_buff *skb2;
 	unsigned int mtu, hlen, left, len, ll_rs;
 	int offset;
@@ -546,8 +545,6 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 	struct rtable *rt = skb_rtable(skb);
 	int err = 0;
 
-	dev = rt->dst.dev;
-
 	/* for offloaded checksums cleanup checksum before fragmentation */
 	if (skb->ip_summed == CHECKSUM_PARTIAL &&
 	    (err = skb_checksum_help(skb)))