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: I9d97f0a3a45dabf1c218c49017de14504bca8f13
Merge branch 'cm-10.2' into martincz