ipmi: reduce polling when interrupts are available

If we're not currently in the middle of a transaction, and if we have
interrupts, there's no real reason to poll the controller more frequently
than the core IPMI code does.  Set the interrupt_disabled flag
appropriately as the interrupt state changes, and make the timeout code
reset itself only if the transaction is incomplete or we have no
interrupts.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>