net: constify struct net_protocol

Remove long removed "inet_protocol_base" declaration.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index db46b4b..6c98b43 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -202,7 +202,7 @@
 	{
 		int protocol = ip_hdr(skb)->protocol;
 		int hash, raw;
-		struct net_protocol *ipprot;
+		const struct net_protocol *ipprot;
 
 	resubmit:
 		raw = raw_local_deliver(skb, protocol);