scsi: ipr: Use pci_irq_allocate_vectors

Switch the ipr driver to use pci_alloc_irq_vectors.  We need to two
calls to pci_alloc_irq_vectors as ipr only supports multiple MSI-X
vectors, but not multiple MSI vectors.

Otherwise this cleans up a lot of cruft and allows to use a common
request_irq loop for irq types, which happens to only iterate over a
single line in the non MSI-X case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>