[NETFILTER]: Fix iptables ABI breakage on (at least) CRIS

[NETFILTER]: Fix iptables ABI breakage on (at least) CRIS

With the introduction of x_tables we accidentally broke compatibility
by defining IPT_TABLE_MAXNAMELEN to XT_FUNCTION_MAXNAMELEN instead of
XT_TABLE_MAXNAMELEN, which is two bytes larger.

On most architectures it doesn't really matter since we don't have
any tables with names that long in the kernel and the structure
layout didn't change because of alignment requirements of following
members. On CRIS however (and other architectures that don't align
data) this changed the structure layout and thus broke compatibility
with old iptables binaries.

Changing it back will break compatibility with binaries compiled
against recent kernels again, but since the breakage has only been
there for three releases this seems like the better choice.

Spotted by Jonas Berlin <xkr47@outerspace.dyndns.org>.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>