phy: add QSGMII and PCIE modes

Prepare for upcoming phys that'll handle QSGMII or PCIe.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>