arm64: dts: marvell: Fix compatible strings for Armada 3720 boards

All Armada 3720 boards have Armada 3720 processor which is of Armada 3700
family and do not have Armada 3710 processor. So none of them should have
compatible string for Armada 3710 processor.

Fix compatible string for all these boards by removing wrong processor
string "marvell,armada3710" and adding family string "marvell,armada3700"
as the last one. (Note that this is same way how are defined Armada 3710
DTS files).
[gclement: fix conflict for v6.2]
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>