cpufreq_ondemand.c: rework touch

- use a "smart" detection for the touch duration
- introduce a min duration for touch to be active
- add a percentage value instead of fixed percentage
- no lower threshold needed anymore
- upper threshold is determined by ((up_threshold - 1) - touch_percent)
- remove wrong comment

Signed-off-by: SkipXS <sskkiipp@gmail.com>