amd-xgbe: Update PCI support to use new IRQ functions

Some of the PCI MSI/MSI-X functions have been deprecated and it is
recommended to use the new pci_alloc_irq_vectors() function. Convert the
code over to use the new function. Also, modify the way in which the IRQs
are requested - try for multiple MSI-X/MSI first, then a single MSI/legacy
interrupt.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>