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

Despite using pci_enable_msi_range, this driver was only requesting a
single MSI vector anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>