netfilter: xt_recent: relax ip_pkt_list_tot restrictions

The maximum value for the hitcount parameter is given by
"ip_pkt_list_tot" parameter (default: 20).

Exceeding this value on the command line will cause the rule to be
rejected.  The parameter is also readonly, i.e. it cannot be changed
without module unload or reboot.

Store size per table, then base nstamps[] size on the hitcount instead.

The module parameter is retained for backwards compatibility.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>