[NETFILTER]: {ip,ip6}_tables: remove some inlines

This patch removes inlines except those which are used
by packet matching code and thus are performance-critical.

Before:

$ size */*/*/ip*tables*.o
   text    data     bss     dec     hex filename
   6402     500      16    6918    1b06 net/ipv4/netfilter/ip_tables.o
   7130     500      16    7646    1dde net/ipv6/netfilter/ip6_tables.o

After:

$ size */*/*/ip*tables*.o
   text    data     bss     dec     hex filename
   6307     500      16    6823    1aa7 net/ipv4/netfilter/ip_tables.o
   7010     500      16    7526    1d66 net/ipv6/netfilter/ip6_tables.o

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>