dt-bindings: arm: stm32: Add Engicam MicroGEA STM32MP1 MicroDev 2.0 7" OF

MicroGEA STM32MP1 is a STM32MP157A based Micro SoM.

MicroDev 2.0 is a general purpose miniature carrier board with CAN,
LTE and LVDS panel interfaces.

7" OF is a capacitive touch 7" Open Frame panel solutions.

MicroGEA STM32MP1 needs to mount on top of MicroDev 2.0 board with
pluged 7" OF for creating complete MicroGEA STM32MP1 MicroDev 2.0
7" Open Frame Solution board.

Add bindings for it.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>