Revert "display: Let the gralloc_priv.h header be overloaded"

This reverts commit 0679a9dae81698c5240c8f21c28a9e8c7a82979f.
Revert "Under CM, always assume kernel source is present"

This reverts commit 352244ae52a2192f9e1ca6629c4f09db956372ba.