Call pte_spill_v() from the real mode fault handler instead of rerolling

Call pte_spill_v() from the real mode fault handler instead of rerolling
it.  This will reduce the number of places to audit for locking.

Note that for profiling purposes pte_spill_v() is now marked a __noprof
since per-CPU profiling buffers are not guaranteed to be 1:1 mapped and
cannot be accessed from the real mode fault handler.

ok kettenis@, deraadt@, dlg@