wifi: Allow Settings to retrieve country code

This makes getCountryCode behave like getFrequencyBand

This allows Settings to get/set country code like
it can for frequency band.

Change-Id: Id9f00d3a678642c6c142fd1511af820d729507a7

Conflicts:
	services/java/com/android/server/WifiService.java
	wifi/java/android/net/wifi/WifiStateMachine.java