Fix for phones that do not support RIL_REQUEST_DATA_REGISTRATION_STATE

Some older phones (inc) do not support reporting data registration status
via RIL_REQUEST_DATA_REGISTRATION_STATE. Instead, this fix allows them
to report via RIL_REQUEST_VOICE_REGISTRATION_STATE.

Change-Id: Ifc546256d2af26f4d9e372d66d6a4a557033af69