audio: update WiredAccessoryManager to use ExtconUEventObserver based on events available

Update WiredAccessoryManager to use ExtconUEventObserver only if
at least one event is available with ExtconUEventObserver

CRs-Fixed: 2444687
Change-Id: I457630428a06016ab71c797efd887f55fcba70c6

Author: Dhananjay Kumar

services/core/java/com/android/server/WiredAccessoryManager.java

@@ -129,7 +129,7 @@ private void onSystemReady() {
         }
 
 
-        if (ExtconUEventObserver.extconExists()) {
+        if (ExtconUEventObserver.extconExists() && mExtconObserver.uEventCount() > 0) {
             if (mUseDevInputEventForAudioJack) {
                 Log.w(TAG, "Both input event and extcon are used for audio jack,"
                         + " please just choose one.");
@@ -713,6 +713,10 @@ private void init() {
 
         }
 
+        public int uEventCount() {
+            return mExtconInfos.size();
+        }
+
         @Override
         public Pair<Integer, Integer> parseState(ExtconInfo extconInfo, String status) {
             if (LOG) Slog.v(TAG, "status  " + status);