The PCI interrupt vectors intended to be associated with a queue may
not start at 0; a driver may allocate pre_vectors for special use. This
patch adds an offset parameter so blk-mq may find the intended affinity
mask and updates all drivers using this API accordingly.

Cc: Don Brace <don.brace@microsemi.com>
Cc: <qla2xxx-upstream@qlogic.com>
Cc: <linux-scsi@vger.kernel.org>
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>