ARM: dts: Add ixp4xx Actiontec MI424WR device trees

ARM: dts: Add ixp4xx Actiontec MI424WR device trees

The Actiontex MI424WR is a pretty widespread home router, made
in many different revisions.

Revisions A, C and D are based on IXP42x. We add a device tree
for the A/C variant and one for the D variant as these differ in
the location of the WAN PHY on the MDIO bus, and the ethernet
interfaces for the WAN PHY and the DSA switch are switched around.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/20250822-ixp4xx-mi424wr-dts-v2-3-cc804884474d@linaro.org