net: ethernet: aquantia: switch to pci_alloc_irq_vectors

pci_enable_msix has been long deprecated, but this driver adds a new
instance.  Convert it to pci_alloc_irq_vectors so that no new instance
of the deprecated function reaches mainline.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Pavel Belous <pavel.belous@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>