Revert "wfd: release wifi p2p resource on disconnecting from WFD service."

This reverts commit fa0aeee678.
Reason for revert: during the disconnection, there are still codes using WifiP2pService.

Bug: 184504089
Test: execute "adb shell setprop persist.debug.wfd.enable 1" and restart the DUT
Change-Id: I0f5a31e072e31fb10f0efe667caa6a6d85942867

services/core/java/com/android/server/display/WifiDisplayController.java

@@ -550,11 +550,6 @@ final class WifiDisplayController implements DumpUtils.Dump {
 
     private void disconnect() {
         mDesiredDevice = null;
-        mWifiP2pManager = null;
-        if (null != mWifiP2pChannel) {
-            mWifiP2pChannel.close();
-            mWifiP2pChannel = null;
-        }
         updateConnection();
     }