netfilter: xtables: use NFPROTO_UNSPEC in more extensions

Lots of extensions are completely family-independent, so squash some code.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --cc net/netfilter/xt_MARK.c
Simple merge

diff --cc net/netfilter/xt_NOTRACK.c
Simple merge

diff --cc net/netfilter/xt_comment.c
Simple merge

diff --cc net/netfilter/xt_mac.c
Simple merge

diff --cc net/netfilter/xt_owner.c
Simple merge

diff --cc net/netfilter/xt_physdev.c
Simple merge

diff --cc net/netfilter/xt_realm.c
Simple merge