pf: put kif into struct pf_pdesc

[kp]

Summary

Put kif and dir into pdesc an use this instead of passing the values
around. This is a mechanical change. Initialize pd2 and use it
where appropriate.
ok henning on an earlier version; ok mpf

Obtained from: OpenBSD, bluhm <[e-mail]>, 47de5c193e
Sponsored by: Rubicon Communications, LLC ("Netgate")