configure ledc to auto select clock

[FelixPe]

• [x] This PR is for the dev-esp32-idf4 branch rather than for the release branch.
• [x] This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• [x] I have thoroughly tested my contribution.
• [x] The code changes are reflected in the documentation at docs/* or do not change any behavior.

To be completed below: Description of and rationale behind this PR.

Added clock configuration according to https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/ledc.html#_CPPv414ledc_clk_cfg_t

Fixes #3558

[pjsg]

Can you also add an invert option to this module that sets the output_invert flag in the ledc_channel_config_t? https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/ledc.html#_CPPv4N21ledc_channel_config_t13output_invertE

Thanks

[jmattsson]

I'm so sorry, I completely missed this PR. While Philip's request is good, I'm going to merge this fix right away as it's already way way overdue.