Check whether support telephony for hearing device call routing

Root Cause: Tablet might not support Call

Solution: Check isVoiceCapable() first

Fix: 270472166
Test: make RunSettingsRoboTests ROBOTEST_FILTER=HearingDeviceCallRoutingPreferenceControllerTest
Change-Id: Icf69d286f63a737941447a6c16a08b4bb8c1fe23
2 files changed