netpoll: Should handle ETH_P_ARP other than ETH_P_IP in netpoll_neigh_reply

The received ARP request type in the Ethernet packet head is ETH_P_ARP other than ETH_P_IP.

[ Bug introduced by commit b7394d24
  ("netpoll: prepare for ipv6") ]
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -550,7 +550,7 @@ static void netpoll_neigh_reply(struct sk_buff *skb, struct netpoll_info *npinfo
 		return;
 
 	proto = ntohs(eth_hdr(skb)->h_proto);
-	if (proto == ETH_P_IP) {
+	if (proto == ETH_P_ARP) {
 		struct arphdr *arp;
 		unsigned char *arp_ptr;
 		/* No arp on this interface */