avr: move timing control from ma_light to sk6812.

This allows for better control over the LED strip. We can now trigger the
LED strip externally (e.g. by setting a new RGBW value).

avr/modules/sk6812/README

@@ -16,6 +16,8 @@ RGB Value for activated light:
 Example:
   Set color of LED strip to blue (half intensity)
   aqhome-tool setdata -N nodes/12345678/RGBWVALUE -v 0x80
+  or in modern format:
+  aqhome-tool setdata -N nodes/12345678/RGBWVALUE -v GREEN:RED:WHITE:BLUE
 
 
 1.2. RGBWSTATE