Revert "More ION ifdeffing"

This reverts commit f312e35bef18be6a659be15b9dc21c1f3e835176.
Revert "hackety hack..."

This reverts commit 0e4cf3b1b405f45ec864c26c43141e11a554ba75.
Revert "display: Use actual kernel headers for all builds"

This reverts commit 08b048681636373e3b987c4a1f78067db093af0f.