dt-bindings: arm: fsl: add toradex,apalis-imx8 et al.

Add toradex,apalis-imx8 for the Apalis iMX8 aka QuadMax modules and the
carrier boards (Apalis Evaluation board as well as Ixora V1.1 and V1.2)
they may be mated in.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>