input: HTC: wake-on-volume support

Referenced HTC kernel m7-jb-3.4.10-e22f38b

Patch set 2) ifdef and Kconfig to limit to MACH_HTC

Change-Id: Ifeacaa74bada9985a936b0f5ac29b0550d5a5122
Merge remote-tracking branch 'upstream/cm-10.2' into cm-10.2