Deduplicate the isIpv6ULA implementation.

Leverage the ConnectivityUtils#isIPv6ULA implementation which is also
accessible for modules, to deduplicate the implementation.

Bug: 183601771
Test: TH
Change-Id: I0943cd76f95e2f54d619015231f68b326194c8b9

framework/src/android/net/LinkAddress.java

@@ -37,6 +37,8 @@ import android.os.Parcelable;
 import android.os.SystemClock;
 import android.util.Pair;
 
+import com.android.net.module.util.ConnectivityUtils;
+
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
@@ -146,11 +148,7 @@ public class LinkAddress implements Parcelable {
      * Per RFC 4193 section 8, fc00::/7 identifies these addresses.
      */
     private boolean isIpv6ULA() {
-        if (isIpv6()) {
-            byte[] bytes = address.getAddress();
-            return ((bytes[0] & (byte)0xfe) == (byte)0xfc);
-        }
-        return false;
+        return ConnectivityUtils.isIPv6ULA(address);
     }
 
     /**