PowerHAL: disable power.msm8960 and rely on default for now

power.msm8960 is useless for the GPRO because it lacks
/dev/socket/mpdecision/touchboost at kernel side which results
in a log flood of errors whenever the screen is touched.
We'll rely on the default powerHAL for now until we figure out
a custom one in the future a la jf-series.

Change-Id: I0c716ce3184e90c08bf15fc58a5d18937f5f1148