Specify explicitly FLAG_IMMUTABLE for PendingIntent

The existing pending intent in the BatteryTipUtils has been specified
FLAG_UPDATE_CURRENT. This change is to add explicitly FLAG_IMMUTABLE
to the pending intent.

Fixes: 171506726
Test: build pass, robotest
Change-Id: Ib82ddb45e05b492eef300f2ec064803d768419d0
1 file changed