Fix CDMA ERI/roaming indicator issues

- If the SID is not in NAM and PRL, the phone should use default Roaming
  Indicator
- If a system is acquired that matches the NAM but does NOT match the PRL,
  the device shall display a FLASHING roaming indicator
- Handle corner cases for PRL is not loaded / Home SID is not programmed
- Reorganize the ERI logic