m7-common: use new offmode_charging and images

HTC incorporated charger functionality into offmode_charging and added
1% increment images. This makes offmode charging look much nicer. Also,
bring back detect_key and power_test so that the power button works to
turn-on the device from offmode.

Blobs from m7wlv 5.28.605.2.

Change-Id: Ic87b2307e88636ffdf0d971c49bed87faf7aa378