ARM: dts: stm32: Add SCMI version of STM32 boards (DK1/DK2/ED1/EV1)

Add a "secure" version based on SCMI of STM32 boards. Only boards
provided by STMicroelectronics are concerned:

-STM32MP157A-DK1
-STM32MP157C-DK2
-STM32MP157C-ED1
-STM32MP157C-EV1

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