nf_nat: fix memset error

This patch fixes an incorrect memset in the NAT code, causing
misbehaviour when unloading and reloading the NAT module.
Applies to stable-2.6.22 and stable-2.6.23.

Please apply, thanks.
[NETFILTER]: nf_nat: fix memset error

Upstream commit e0bf9cf1

The size passing to memset is the size of a pointer. Fixes
misbehaviour when unloading and reloading the NAT module.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>