ucm2:sof-soundwire: Add Support For Dell Privacy Mic Mute LED Control

[GitHub issues - opened]

alsa-project/alsa-ucm-conf issue #59 was opened from GoPerry:

Dell is going to add internal microphone mute led control for Dell privacy system,
which has hardware level protection for audio privacy, when mic mute
state is changed, the ucm2 will help to switch the Mic Mute LED state.

This solution has been discussed by this FR.
https://github.com/thesofproject/linux/issues/2496

This system EC which support audio privacy needs get ACK event when the LED state need to change.
I add one new mixer for RT715 (local mics) to switch the mic mute led state
So the UCM2 will help to call the mixer to notify the LED state is changed.
The led trigger driver will emit the notification to EC through the  LED driver.
Then LED state controlled by the EC will be changed accordingly.

Issue URL     : https://github.com/alsa-project/alsa-ucm-conf/issues/59
Repository URL: https://github.com/alsa-project/alsa-ucm-conf