Update MobileNetworkTypeTile.java

jira:2098
2g 3g toggle not working for CM10.2. A fix has been merged in settings when "2g only" checkbox wasn't working. The same change needs to be replicated for this SystemUI tile. It's basically because of the "no-longer-supported" constant "NT_MODE_WCDMA_PREF". Migration to "NT_MODE_LTE_GSM_WCDMA" is suggested.