[5G PCO]The PCO's contents is not fixed, so catch the last byte.

The each of chips can report different PCO content value.
some chips report the value only. some chips report Mccmnc+value.
For example:
case1: contents: mccmnc1
case2: contents: 1
Therefore, here modifies the code to get the last value.

Bug: 202952410
Test: atest NetworkTypeControllerTest (PASS)
Change-Id: Iec3fb2ba1e8ed811c5e111e576ecb172a33bd52e