ARM: dts: armada-38x add node labels

As was done with Armada XP, add node labels to Armada 38x common and SoC
specific nodes to make them easier to reference in board device trees.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>