netfilter: ipset: deinline ip_set_put_extensions()

On x86 allyesconfig build:
The function compiles to 489 bytes of machine code.
It has 25 callsites.

    text    data       bss       dec     hex filename
82441375 22255384 20627456 125324215 7784bb7 vmlinux.before
82434909 22255384 20627456 125317749 7783275 vmlinux

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
CC: Eric W. Biederman <ebiederm@xmission.com>
CC: David S. Miller <davem@davemloft.net>
CC: Jan Engelhardt <jengelh@medozas.de>
CC: Jiri Pirko <jpirko@redhat.com>
CC: linux-kernel@vger.kernel.org
CC: netdev@vger.kernel.org
CC: netfilter-devel@vger.kernel.org
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>