phy: mvebu-cp110-comphy: convert to use eth phy mode and submode

Convert mvebu-cp110-comphy PHY driver to use recently introduced
PHY_MODE_ETHERNET and phy_set_mode_ext().

Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Maxime Chevallier <maxime.chevallier@bootlin.com>
Cc: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>