Telephony: Add getLteOnGsmMode() method (2/2)

Same functionality as the existing getLteOnCdmaMode, but for GSM
LTE devices.
Enable with the telephony.lteOnGsmDevice system property

From CM 10.0: Ibfb47ca608e51393b99d3308e0a6c66050b3f32e
- Moved getLteOnGsmModeStatic() to TelephonyManager.
telephony: Use reflection to create command interface (RIL class)

Change-Id: Icdc02eaa74b89dbde4ddfb989cc62481d6423312

Conflicts:
	src/java/com/android/internal/telephony/PhoneFactory.java