genwqe: use pci_irq_allocate_vectors

Simply the interrupt setup by using the new PCI layer helpers.

One odd thing about this driver is that it looks like it could request
multiple MSI vectors, but it will then only ever use a single one.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Acked-by: Frank Haverkamp <haver@linux.vnet.ibm.com&gt;=>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>