[PORT FROM GB] Add support for dynamically adjusting volume during the call in S3...

[PORT FROM GB] Add support for dynamically adjusting volume during the call in S3 state

BZ: 13269

This patch fix the problem that can not adjust the volume during the
call in S3 state with screen off because of the proximity sensor. By
adding sysfs interface "enabled_wakeup" and "disabled_wakeup" in
gpio-keys to dynamically enable or disable the gpiokeys.

Change-Id: I80c45daca2999821502302998f76e0e54c806a68
Signed-off-by: Shijie Zhang <shijie.zhang@intel.com>
Reviewed-on: http://android.intel.com:8080/26773
Reviewed-by: Barthes, FabienX <fabienx.barthes@intel.com>
Tested-by: Barthes, FabienX <fabienx.barthes@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>