netfilter: ctnetlink: Make some parameters integer to avoid enum mismatch

Not all parameters passed to ctnetlink_parse_tuple() and
ctnetlink_exp_dump_tuple() match the enum type in the signatures of these
functions. Since this is intended change the argument type of to be an
unsigned integer value.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>