phy: mvebu-cp110-comphy: Rename the macro handling only Ethernet modes

Before adding support for other PHY modes (not Ethernet ones), let's
rename the MVEBU_COMPHY_CONF macro to a more specific (and shorter)
appellation.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>