MFC r266772:
Various cleanups and fixes including switching from timeout to callout

Sponsored by:	Multiplay
MFC r267290:
Make the hpt27xx(4) driver MPSAFE

Sponsored by:	Multiplay
MFC r269613:
Various fixes to hptnr(4)

Sponsored by:	Multiplay
MFC r269615:
Various fixes to hptrr(4)

Sponsored by:	Multiplay