Define new network scan RIL API

This CL defines the RIL API for network scan and also includes dummy
stubs for the new API.

Test: Telephony Sanity Test
Bug: 30954762
Change-Id: Id276ca35d399c6860dc5f6413991ddf0ab3fd5e5
diff --git a/libril/ril_commands.h b/libril/ril_commands.h
index 6518a4e..de73936 100644
--- a/libril/ril_commands.h
+++ b/libril/ril_commands.h
@@ -156,3 +156,5 @@
     {RIL_REQUEST_SET_UNSOLICITED_RESPONSE_FILTER, radio::setIndicationFilterResponse},
     {RIL_REQUEST_SET_SIM_CARD_POWER, radio::setSimCardPowerResponse},
     {RIL_REQUEST_SET_CARRIER_INFO_IMSI_ENCRYPTION, radio::setCarrierInfoForImsiEncryptionResponse},
+    {RIL_REQUEST_START_NETWORK_SCAN, radio::startNetworkScanResponse},
+    {RIL_REQUEST_STOP_NETWORK_SCAN, radio::stopNetworkScanResponse},