mdss: implement panel color control

Adapted and modified work by CM-10.2, morfic and ktoonsez
- what a pain this was to make it work on hlte

    Creates a syfs interface here:
	/sys/class/lcd/panel/panel_colors

    Will accept 0-4 for parameters:
      0 - Cold (more blues)
      1 - Cool
      2 - Normal (stock colors)
      3 - Warm
      4 - Hot (more reds)

Signed-off-by: Paul Reioux <reioux@gmail.com>