[telephony] Fixed sgianl strength issue

The flag GSM of signal strength maybe unknown under OOS, but the signal
strength changed has been notified. In this case, set the flag GSM based
on the signal strength data.

Test: manual
Bug: 62431424

Change-Id: Ic400faf8f480f5d8dd0f79342e34f94a2deaa4e2
1 file changed