SamsungQualcommUiccRIL: use signalstrength value instead of # of bars

  * Math error in GSM level calculation gave high probability that 4
    Samsung bars would be shown as 3 AOSP bars.
  * Samsung sends # of bars in the signalstrength field of GSM and LTE,
    indexes 0 and 7. But this is on a 0-5 scale where AOSP uses 0-4 scale.
    The cutoff points for the bins are also different. Because of this
    confusion, just pass the measured signalstrength to the framework
    instead of computing signalstrength based on # of Samsung bars.
  * For debug and experimentation, Samsung's bar method can be enabled
    by setting telephony.sends_barcount=true

Change-Id: I8238af83f3a597b32eb99f42c71cbc263ad5bc82