TD-SCDMA signal strength support for Samsung Qualcomm device.

Introduce a new value TdScdmaSignalStrength of device property ro.telephony.ril.v3,
it indicates the signal strength Parcel reported by rild contains TdScdmaRscp field.
The old approach doesn't work well when device switch between GSM and TD-SCDMA network.
Because system property TelephonyProperties.PROPERTY_DATA_NETWORK_TYPE is not set correctly
before SamsungQualcommRIL.esponseSignalStrength(Parcel p) is called.

Change-Id: I4b4c098de353a43fc83a42ba6b37a0017db13c22