- Use the existing driver lock in cdevsw methods and remove D_NEEDGIANT.
- Use callout(9) instead of timeout(9).
- Use bus_*() instead of bus_space_*().
- Don't check for a NULL softc in attach.

Tested by:	no one
Extend earlier addition of stack frames to most of support.S.  This makes
stack traces in KDB, HWPMC, and DTrace much more reliable and useful.

Reviewed by:	kan, kib
Obtained from:	Netflix, Inc.
MFC after:	5 days