net: thunderx: Switch to pci_alloc_irq_vectors

Remove deprecated pci_enable_msix API in favour of its
successor pci_alloc_irq_vectors.

Signed-off-by: Thanneeru Srinivasulu <tsrinivasulu@cavium.com>
Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>