ipm: Add support for stm31mp157c_dk2 board
ipm: Add support for stm31mp157c_dk2 board

Add the mailbox support for the stm32mp15c_dk2,
relied on IPCC peripheral.

Signed-off-by: Arnaud Pouliquen <b379f9d268ae6bc79bae62bbf7d1708239982b68@st.com>

finikorg/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr