scsi: aacraid: switch to pci_alloc_irq_vectors

Use pci_alloc_irq_vectors and drop the hand-crafted interrupt affinity
routines.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Cc: Adaptec OEM Raid Solutions <aacraid@microsemi.com>
Reviewed-by: Raghava Aditya Renukunta <raghavaaditya.renukunta@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>