Do not report error on device disconnected

A device disconnection (when the adb connection is closed) makes the
read() on the "receiver" socket fail.

Since commit 063a8339ed, this is reported
as an error. As a consequence, scrcpy fails with:

    ERROR: Controller error

instead of:

    WARN: Device disconnected

To fix the issue, report a device disconnection in that case.

PR #5044 <https://github.com/Genymobile/scrcpy/pull/5044>

app/src/controller.h

@@ -28,7 +28,8 @@ struct sc_controller {
 };
 
 struct sc_controller_callbacks {
-    void (*on_error)(struct sc_controller *controller, void *userdata);
+    void (*on_ended)(struct sc_controller *controller, bool error,
+                     void *userdata);
 };
 
 bool