stm32/led: Support PWM output without TIM3.
stm32/led: Support PWM output without TIM3.

For example, the STM32WB55 doesn't have TIM3 but can still drive LEDs using
PWM on other timers.

pramasoul/micropython,pramasoul/micropython,bvernoux/micropython,adafruit/circuitpython,MrSurly/micropython,adafruit/circuitpython,pramasoul/micropython,adafruit/circuitpython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,henriknelson/micropython,adafruit/circuitpython,pramasoul/micropython,MrSurly/micropython,MrSurly/micropython,henriknelson/micropython,MrSurly/micropython,adafruit/circuitpython,henriknelson/micropython,MrSurly/micropython,pramasoul/micropython,adafruit/circuitpython,bvernoux/micropython,henriknelson/micropython,bvernoux/micropython