pf: remove unused ioctls.

[will]

Summary

Several ioctls are unused in pf (in the sense that no base utility
references them). Additionally, a cursory review of pf-based ports
indicates they're not used elsewhere either. Some of them have been
unused since the original import. As far as I can tell, they're also
unused in OpenBSD. Finally, removing this code removes the need for
future pf work to take them into account.

Test Plan

Build, install, run pf.

[kp]

Looks good. Thanks for this. Let's get it in before 12.