ARM: mvebu: add support for Allied Telesis x530

This is a range of stackable network switches. The SoC is Armada-385 and
there are a number of variants with differing network port
configurations. The DP variants are intended for a harsher operating
environment so they use a different i2c mux and fit industrial-temp
parts.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Stefan Roese <sr@denx.de>