ARM: dts: stm32: Add Engicam i.Core STM32MP1 SoM

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

General features:
- STM32MP157A
- Up to 1GB DDR3L
- 4GB eMMC
- 10/100 Ethernet
- USB 2.0 Host/OTG
- I2S
- MIPI DSI to LVDS
- rest of STM32MP157A features

i.Core STM32MP1 needs to mount on top of Engicam baseboards
for creating complete platform solutions.

Add support for it.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>