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: NChristoph Hellwig <hch@lst.de>
Acked-by: NGabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Acked-by: Frank Haverkamp <haver@linux.vnet.ibm.com>=
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>