[NETFILTER]: xt_iprange: fix typo in address family

The family for iprange_mt4 should be AF_INET, not AF_INET6.
Noticed by Jiri Moravec <jim.lkml@gmail.com>.

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