Ported Keyboard stuff from tf700 as per this commit: https://github.com/CyanogenMod/android_device_asus_tf300t/commit/0b6321c5226d9ae76d0b7d968f88bdcfbc7ff4fc

This fixes hardware keys and dual battery indicator.

Change-Id: I74643be9e3e62d1ab46f10779440394862057b0f