netfilter 04/09: x_tables: fix match/target revision lookup

Commit 55b69e91 (netfilter: implement NFPROTO_UNSPEC as a wildcard
for extensions) broke revision probing for matches and targets that
are registered with NFPROTO_UNSPEC.

Fix by continuing the search on the NFPROTO_UNSPEC list if nothing
is found on the af-specific lists.

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