Added offscreen gesture support

Currently only oppo devices support this
To enable use overlay
    <bool name="config_offscreenGestureSupport">true</bool>

Offscreen gestures are gestures drawn on the screen
when off. Oppo supports the following gestures
V, circle, II, <, >, double tap

The default mapping form oppo are
V - toggle torch
circle - start camera
II - play/pause musiv
> - next track
< - previous track

This gestures are reported as keys F3,F4,F5,F6,F7,F8

This change also switches to the oppo dt2w implementation
in kernel.

This also adds the base support for volume key music track
control since this is sharing the same code

Change-Id: I89914d7ecc25dd1e13e60793233ee0db8dd1feed