Connect up a QUEUE FULL event with CAM and adjust openings.

Unfortunately, the QUEUE FULL event only tells you Bus && Target.
It doesn't tell you lun. In order for the XPT_REL_SIMQ action to
work, we have to have a real lun. But which one? For now, just
iterate over MPT_MAX_LUNS.

Practically speaking, this is only going to be happening for lower
quality SAS or SATA drives behind the SAS controller, which means
only lun 0, so it's not so bad.

Helpful Reminder Nagging from: John Baldwin, Fred Whiteside

MFC after: 5 days