Telephony: Consider EVDO ecio zero value as valid.
When mEvdoEcio receives 0 getEvdoEcio returns -1.

Ecio valid values are positive integers, to fix this
consider EVDO ecio zero value as valid.

Change-Id: Ice8415150e7502c7f39e1a4135d35ea2bec1eb1f
CRs-Fixed: 402159