Retire pmtimer driver. Move time fixing into apm driver. Move
Iwasaki-san's copyright over. Remove FIXME code that couldn't possibly
work. Call tc_settime() with our estimate of the delta we've been
alseep (the one we print) to adjust the time. Not sure what to do
about callouts, so keep the small #ifdef in place there.

Differential Revision: https://reviews.freebsd.org/D13823