Fixed stylus eraser being rejected by palm rejection

The stylus eraser appeared not to work, i.e. Android did not respond to
input from the eraser. It turned out that all input except stylus input
is rejected when palm rejection is activated. The problem was that the
eraser itself activates palm rejection when it hovers. The solution is
to allow the eraser during palm rejection. This solution makes sense
because the eraser input works in the exact same way as normal stylus
input.

Change-Id: I90824500be7613af4f00427c59ce828528b632f7
Merge remote-tracking branch 'cm/android-4.4' into android-4.4