Rearrange interrupt register processing for 2200s.  The mailbox semaphore seems to be disconnected from the interrupt status register, so we shouldn't wait until the interrupt status is nonzero to check it.  This makes onboard FC controllers in Sun systems work better.
Rearrange interrupt register processing for 2200s.  The mailbox semaphore
seems to be disconnected from the interrupt status register, so we shouldn't
wait until the interrupt status is nonzero to check it.  This makes onboard
FC controllers in Sun systems work better.

tested on a blade1k (by kettenis@) and a v880.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars