scsi: megaraid_sas: switch to pci_alloc_irq_vectors

[mkp: fixed bad indentation]

Signed-off-by: Hannes Reinecke <hare@suse.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>