netfilter: xt_connmark: do not cast xt_connmark_tginfo1 to xt_connmark_tginfo2

These structures have different layout, fill xt_connmark_tginfo2 with
old fields in xt_connmark_tginfo1. Based on patch from Jack Ma.

Fixes: 472a73e0

 ("netfilter: xt_conntrack: Support bit-shifting for CONNMARK & MARK targets.")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>