gpio: add wakeup source trace in GPIO driver

gpio: add wakeup source trace in GPIO driver

BZ: 23641

Add logs to trace the wakeup source at each time the langwell-gpio
device resumes.

Change-Id: I8774526d1a529205c8c4681a20ba6a4beac6065f
Signed-off-by: Li, Ning <ning.li@intel.com>
Reviewed-on: http://android.intel.com:8080/35387
Reviewed-by: Yang, Bin <bin.yang@intel.com>
Reviewed-by: Du, Alek <alek.du@intel.com>
Reviewed-by: Mansoor, Illyas <illyas.mansoor@intel.com>
Tested-by: Wang, Zhifeng <zhifeng.wang@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>