gpu control: internal apply voltage changes as deltas to default voltage.
if one lowers voltage of i.e lowest step by 25mv compared to default voltage, this delta again gets applied after freq of lowest step gets changed.
all voltage deltas are shown in /sys/class/misc/gpu_control/gpu_voltage_delta.
all voltage deltas are reset by: echo 1 > /sys/class/misc/gpu_control/gpu_voltage_delta

Change-Id: I205aaacbda7b520575c795990d685e0e4b9893ed