Revert "allow forcing HighEndGfx mode"

I have a feeling this is breaking certain areas of the OS where transparency is used

This reverts commit 3e1c38bd7c238b07ed873574c972d9df805664e1.

Change-Id: I0704a502b19ecaa55ec534b2f5de81b7ed92497d
Revert "ActivityManager: Memoize graphics acceleration check"

This reverts commit 86445d0f9173e56fd384d4e98f2df63b059a3b2f.
allow forcing HighEndGfx mode

people have already started fipping the lomRam prop to enable
transparent status bar, this will enable it with fewer
repercussions

Change-Id: Ib76a901d66ea52a5225fe7f0135f6fa6516c2e5f