dts: arm: gigadevice: gd32f4xx: add timer and pwm nodes
dts: arm: gigadevice: gd32f4xx: add timer and pwm nodes

Add timer and pwm nodes. The structure follows a similar approach to the
one used by STM32. Timer nodes store all timer information (e.g.
pre-scaler), whereas the pwm nodes are children of the timer node
indicating a specialization of the multiple timer functionalities.

Signed-off-by: Gerard Marull-Paretas <76c1da08be458687d0066397d08e4f7ea9894377@teslabs.com>

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