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

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.

MicroGEA STM32MP1 needs to mount on top of this MicroDev 2.0 board
for creating complete MicroGEA STM32MP1 MicroDev 2.0 Carrier board.

Add bindings for it.

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