exynos: Disable CPU caching
exynos: Disable CPU caching

Having migrated away from UMP, cache control must now be implemented by
the DRM drivers themselves, and we haven't done this for Exynos.
Disable use of the CPU cache there to avoid visual glitches.
This will result in a performance drop.

commshare/xf86-video-armsoc,commshare/xf86-video-armsoc,Popolon/xf86-video-armsoc,Popolon/xf86-video-armsoc