cciss: make interrupt access methods return type bool

Change the return type of our interrupt access routines to bool from
unsigned long.  It makes more sense that way.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Cc: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>