Comment 0 for bug 1965846

[Impact]
On Dell's XPS 9315, the MIC-Mute function is working but the LED(on F4) state is changed accordingly.

[Fix]
Dell's mic mute support in privacy mode has been upstream, but the the mic-mute led
support is still SAUCE patch which is maintained with DMI based quirk. Add a new SKU
for XPS 9315 until Dell's official fix for the mic-mute led.

[Test Case]
1. press mic-mute hot-key and check if mic-mute is enabled or not by the OSD icon.
2. The mic-mute led should be on when mic-mute enabled, off when disabled.

[Where problems could occur]
It's only working on the particular SKU defined in DMI table. Will need to drop it
when Dell release the official solution.