[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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index fb4d779..cafb35a 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -784,10 +784,6 @@
 	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;