Add identifier to the log message

- PmLog messages will have identifier "[pmlog]".

[GF-6756] pmloglib: Add identifier to pmlog message to ...

Open-webOS-DCO-1.0-Signed-off-by: Hongjeon Ha <hj.ha@lge.com>

Change-Id: I53b139585dd7466903697473a4e72015cb6835e3