telephony: Query LTE thresholds from CarrierConfig

config_lteDbmThresholds is not used anymore in P.
CarrierConfig stores only 4 thresholds, ignoring two
"unknown" ones, as they should always equal -44 and 140,
so let's fix our code and move to this.

Change-Id: I0d8a59d5310b001b3da9718e8f286c190269509c
1 file changed