MFC r263248 & r263257: In intr_event_handle() we already save and set
td_intr_frame, so don't do it also in ia64_handle_intr().
Merge r268071, 268072, 268088

 Refactor some code in mps.c to reduce header pollution.
 Add accessor functions for manipulating the CAM CCB status field.
 Don't overload the CCB status field within the driver.

Reviewed by:    gibbs, slm
Obtained from:  Netflix, Inc.
MFC r263253: Don't use the ITC as the faulting address for external
interrupts.
MFC r263254: Move the implementation of kdb_cpu_trap() from <machine/kdb.h>
to machdep.c.