cypress-touchkey: remove backlight timeout feature

Userspace implementation:
http://review.cyanogenmod.org/48796
http://review.cyanogenmod.org/48872
http://review.cyanogenmod.org/48884

Change-Id: Id4ac50168220310e82aa4aae367dad4e72e3a9c3
Merge branch 'cm-10.2' into martincz