Shutdown the card when a catastrophic error occurs. This quenches
any interrupts stemming from the card.
aic7xxx_inline.h:
Return instead of processing additional interrupt state
after handling a catastrophic error. We now shutdown the
chip in this case in the hopes that the system can live
without this controller. The shutdown process invalidates any
other interrupt state.
aic7xxx.seq:
Only attempt to clear SCSIBUSL on Ultra2 controllers. The
clearing is workaround for a selection timeout bug on U2/U160
controllers and happens to be illegal on aic7770 (EISA/VL)
controllers.