netfilter: xt_IDLETIMER: clean up some indenting

These lines were indented wrong so Smatch complained.
net/netfilter/xt_IDLETIMER.c:81 idletimer_tg_show() warn: inconsistent indenting

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>