dt-bindings: arm: stm32: add STM32MP157F-DK2 board compatible

dt-bindings: arm: stm32: add STM32MP157F-DK2 board compatible

Add the "st,stm32mp157f-dk2" compatible string to the STM32 SoC
bindings. The MP157F is functionally similar to the MP157C.

Signed-off-by: Himanshu Bhavani <himanshu.bhavani@siliconsignals.io>
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250603-stm32mp157f-dk2-v2-6-5be0854a9299@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>