Various fixes to hptrr(4):

• Use the existing vbus locks instead of Giant for the CAM sim lock.
• Use callout(9) instead of timeout(9).
• Mark the interrupt handler MPSAFE.
• Don't attempt to pass data in the softc from probe() to attach().
• Remove compat shims for FreeBSD versions older than 8.0.

Reviewed by: Steve Chang <ychang@highpoint-tech.com>