dts: bindings: fix label properties for pwm-leds node
dts: bindings: fix label properties for pwm-leds node

This patch adds a label property to the PWM LED parent node and fixes
the label property description of the child node. Indeed it is the label
of a parent node which can be used as device_get_binding() parameter to
retrieve the LED device, and not the one of a child node.

Fixes #34275

Signed-off-by: Simon Guinot <3ab4e30ada880520f74922b979fc5ca34d9375bb@seagate.com>

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