ARM: dts: armada388-clearfog: add missing phy-modes

The DSA framework has got more picky about always having a phy-mode,
particularly for the CPU port. Add the missing phy-mode properties
for every port which does not have an integrated PHY.

Add a phy-mode property to the ethernet interface facing the switch
as this was configured using SGMII - as the switch is actually
using 1000base-x, let's have some consistency between the two link
partners.

Additionally, the cpu label has never actually been used in the
binding, so remove it.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>