hotspot2: register Passpoint related intents as protected broadcast

These intents should only be broadcast by the System Service, so
register them as protected broadcast.

Bug: 36655814
Test: Build with go/aog/355397, verify in logcat that no non-protected
      broadcast error gets thrown when
      android.net.wifi.action.PASSPOINT_OSU_PROVIDERS_LIST intent
      is broadcasted

Change-Id: I57849d0decef407624cac380a0f12f5428e0f1de