Add sysfs support

sysfs will turn on torch way faster than camera app.
As it isn't supported on all devices we keep using camera by default.
The developer that want to make use of sysfs should make an overlay to edit the path (if necessary) and enable it, like I did here: https://github.com/t4n017/android_device_samsung_janice/commit/9c671ba9a05460e137ed265d9ec1667d3aaabdf7

Change-Id: I0f7c5989e50871680d141dca150a2722b167ca9e