phy: mvebu-cp110-comphy: Add RXAUI support

Add support for RXAUI mode by adding an entry in the COMPHY modes list.

There is no user for this mode yet so we can enforce an up-to-date
firmware and return an error otherwise without breaking anywone.

Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
[miquel.raynal@bootlin.com: adapt the content to the mainline driver]
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>