dts: imx8ml_m7: add mailbox node for NXP i.MX8M Plus SoC
dts: imx8ml_m7: add mailbox node for NXP i.MX8M Plus SoC

Add a device tree node for the messaging unit found on i.MX8M Plus SoCs.

Signed-off-by: Matthias Fend <7eb2758b7ea83d049c149deecb1d9b32b9d92e46@emfend.at>

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