hpilo: add interrupt handler

Add interrupt handler to hpilo.  This is enablement for poll handler,
and it also simplifies the logic for handling an iLO reset, because now
only the interrupt handler needs to look for reset, the file system
interfaces only need to return failure when a reset has happened.

Signed-off-by: David Altobelli <david.altobelli@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>