Add ncid to CellLocation in CellIdentityNr

Update GsmCellLocation documentation for NR case. Since the NR cell ID
is 36 bits and can't fit into the 32-bit field in GsmCellLocation,
return -1 for the CID.

Test: atest CellIdentityNrTest
Bug: 166514842
Change-Id: Ib894e83900b590c11221502ad039781cea5b571c

telephony/java/android/telephony/CellIdentityNr.java

@@ -126,7 +126,11 @@ public final class CellIdentityNr extends CellIdentity {
     @NonNull
     @Override
     public CellLocation asCellLocation() {
-        return new GsmCellLocation();
+        GsmCellLocation cl = new GsmCellLocation();
+        int tac = mTac != CellInfo.UNAVAILABLE ? mTac : -1;
+        cl.setLacAndCid(tac, -1);
+        cl.setPsc(0);
+        return cl;
     }
 
     @Override

telephony/java/android/telephony/gsm/GsmCellLocation.java

@@ -55,7 +55,7 @@ public class GsmCellLocation extends CellLocation {
     }
 
     /**
-     * @return gsm cell id, -1 if unknown, 0xffff max legal value
+     * @return gsm cell id, -1 if unknown or invalid, 0xffff max legal value
      */
     public int getCid() {
         return mCid;