msm8960-common: allow variable button light brightness

Change-Id: Iddec361b707716e21c8890fcb53dfd85df816a52
Merge "msm8960-common: allow variable button light brightness" into cm-10.2
msm8960-common: allow variable button light brightness

Summary:
Change-Id: Iddec361b707716e21c8890fcb53dfd85df816a52

Merge "msm8960-common: allow variable button light brightness" into cm-10.2

Merge remote-tracking branch 'cm/cm-10.2' into merge_cm

Test Plan: confirm on other htc 8960 devices

Reviewers: jriordan001

Differential Revision: http://review.codefirex.com/D480