netfilter: ipset: avoid use of kernel-only types

netfilter: ipset: avoid use of kernel-only types

commit 5276e16bb6f35412583518d6f04651dd9dc114be upstream.

When using the xt_set.h header in userspace, one will get these gcc
reports:

ipset/ip_set.h:184:1: error: unknown type name "u16"
In file included from libxt_SET.c:21:0:
netfilter/xt_set.h:61:2: error: unknown type name "u32"
netfilter/xt_set.h:62:2: error: unknown type name "u32"

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>