Leave touch panel powered on during incall proximity blanking

Neither double tap not touch events are generated, but the touch panel
is kept powered on. This makes the touch detection work more reliably
when display is unblanked again - which in turn makes it more likely
that we can block ui from seeing stray touch events if proximity sensor
is briefly uncovered while phone is at ear.

Previously there was a prototype kernel side implementation that used
single sysfs control path for setting both double tap and sleep mode.
Now there are separate control files and logic is adjusted accordingly.

[mce] Leave touch panel powered on during incall proximity blanking. Fixes JB#17155
Merge pull request #153 from spiiroin/in_call_touch_state

Leave touch panel powered on during incall proximity blanking