LGEStarRIL: Ignore SCREEN_ON/SCREEN_OFF events on star

Logic is taken directly from the p99x stock ROMs: SCREEN_OFF causes
the radio to stop genereating events, including the CBC batt refreshes.

This causes the battery to stop updating while the screen is off.

Change-Id: Iae78cde0442832d985a782d9ed1bb6d59223f234