Add missing UARFCN Getter to CellIdentityTdscdma

Add a method to get the UARFCN for CellIdentityTdscdma.
There is an equivalent method in all the other classes,
so this is simply correcting an oversight.

Bug: 123957505
Test: atest CellIdentityTdscdmaTest
Change-Id: I743d90b4532b86edb34d267ae55eca73de2a0086

api/current.txt

@@ -42350,6 +42350,7 @@ package android.telephony {
     method public String getMccString();
     method public String getMncString();
     method @Nullable public String getMobileNetworkOperator();
+    method public int getUarfcn();
     method public void writeToParcel(android.os.Parcel, int);
     field public static final android.os.Parcelable.Creator<android.telephony.CellIdentityTdscdma> CREATOR;
   }

telephony/java/android/telephony/CellIdentityTdscdma.java

@@ -141,6 +141,14 @@ public final class CellIdentityTdscdma extends CellIdentity {
         return mCpid;
     }
 
+    /**
+     * @return 16-bit UMTS Absolute RF Channel Number,
+     *         {@link android.telephony.CellInfo#UNAVAILABLE UNAVAILABLE} if unavailable.
+     */
+    public int getUarfcn() {
+        return mUarfcn;
+    }
+
     /** @hide */
     @Override
     public int getChannelNumber() {