scsi: smartpqi: switch to pci_alloc_irq_vectors

Which cleans up a lot of the MSI-X handling, and allows us to use the
PCI IRQ layer provided vector mapping, which we can then expose to
blk-mq.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Don Brace <don.brace@microsemi.com>
Tested-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>