arch: arm: dts: Remove disabled marvell,dsa properties

These have been disable since the change to probe Marvell Ethernet
switches as MDIO devices. Remove the properties now that the code to
suppport them will also be removed soon.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>