stingray: use own RIL class

This adds an icc handler for when the radio is turned on, to
select the correct subscription source (RUIM, not NV).

Borrowed bits from SamsungCDMAQualcommRIL (Ib0a0c7f03).

Change-Id: Ie11e5e68b1d81e67807c213d8e0fa6dc9c5db75f
stingray: cleanup CDMA subscription prop

Change-Id: I69e44244d8aa46a829919e093a460529c4e285c2