dt-bindings: arm: fsl: Add Engicam i.Core MX8M Plus EDIMM2.2 Starter Kit

i.Core MX8M Plus is an EDIMM SoM based on NXP i.MX8M Plus from Engicam.

EDIMM2.2 Starter Kit is an EDIMM 2.2 Form Factor Capacitive Evaluation
Board from Engicam.

i.Core MX8M Plus needs to mount on top of this Evaluation board for
creating complete i.Core MX8M Plus EDIMM2.2 Starter Kit.

Add bindings for it.

Signed-off-by: Manoj Sai <abbaraju.manojsai@amarulasolutions.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>