Fix for Signal bars on Samsung devices

Sometimes the CDMA ecio value is sent as a negative integer where we would expect a positive.
This causes SignalStrength.java to mark ecio as -160 (Unknown_Signal_Strength) and making signal bar
s clear out.
This "fix" checks the ecio value and takes it absolute value if it is negative.

Confirmed working on SCH-I500 and SPH-D710

Change-Id: Ic515dd6c92193cd5db75adf5bef93ecd617a5c6a