Minor cleanups:

Minor cleanups:
- remove unused pmap_vp_remove function.
- remove obviously not-applying-to-this-situation comment in
  _pmap_kenter_pa(), copied from pmap_enter() (where it is legit).
- make the PTED_xxx accessors inline.
- actually use PTED_WIRED() rather than inlining it everywhere.

ok mpi@ kettenis@