overlay: Make Sprint specific overlay stuff mcc/mnc exclusive

Change-Id: I6019e81019da4f00c43f00c537dc694e957c3890

Conflicts:
	overlay/frameworks/base/core/res/res/values/config.xml
	overlay/services/Telephony/res/values/config.xml

	new file:   overlay/frameworks/base/core/res/res/values-mcc310-mnc120/config.xml
	modified:   overlay/frameworks/base/core/res/res/values/config.xml
	new file:   overlay/services/Telephony/res/values-mcc310-mnc120/config.xml
	new file:   overlay/services/Telephony/res/values/config.xml