dt-bindings: arm: stm32: Add Engicam i.Core STM32MP1 C.TOUCH 2.0

i.Core STM32MP1 is an EDIMM SoM based on STM32MP157A from Engicam.

C.TOUCH 2.0 is a general purpose carrier board with capacitive
touch interface support.

i.Core STM32MP1 needs to mount on top of this Carrier board for
creating complete i.Core STM32MP1 C.TOUCH 2.0 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>