[NETFILTER]: arp_tables: remove ipchains compat hack

Remove compatiblity hack copied from ip_tables.c - ipchains didn't even
support arp_tables :)
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/netfilter/arp_tables.c

@@ -784,10 +784,6 @@ static int do_replace(void __user *user, unsigned int len)
 	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
 		return -EFAULT;
 
-	/* Hack: Causes ipchains to give correct error msg --RR */
-	if (len != sizeof(tmp) + tmp.size)
-		return -ENOPROTOOPT;
-
 	/* overflow check */
 	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
 		return -ENOMEM;