dts: stm32l4+: add bindings for dmamux
dts: stm32l4+: add bindings for dmamux

Add device tree bindings for dmamux in stm32l4+ soc.

Signed-off-by: Shlomi Vaknin <54c0a9b681c5459019f43c3dc65e0278ef9673d9@gmail.com>

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