[Intel-gfx] Legacy gamma table updates broken in 4.7-rc4

[Mario Kleiner]

A strange one. In Linux 4.7-rc4, at least as build by the Ubuntu 
mainline ppa, gamma table updates via RandR don't work. No errors are 
reported and the X-Server thinks everything went well, but on Intel 
Ironlake and Ivybridge the updates don't have any visual effect.

The same problem doesn't happen with current drm-next, so something was 
fixed. Looking at the new code in intel_color.c i can't see anything 
obvious that would break it on 4.7-rc but make it work on drm-next?

Are there some gamma fixes in drm-next that didn't make it into 4.7-rc yet?

Thanks,
-mario