ecore_wl2: Fix small bug in flush handler

If wl_display_flush() returns a non negative number it was successful,
so we should disable the write handler then.  We were theoretically always
doing an extra flush on an empty buffer.

This is mostly cosmetic as that's not a costly operation.

src/lib/ecore_wl2/ecore_wl2_display.c

@@ -514,7 +514,7 @@ _cb_connect_data(void *data, Ecore_Fd_Handler *hdl)
      {
         ret = wl_display_flush(ewd->wl.display);
         code = errno;
-        if (ret == 0)
+        if (ret >= 0)
           ecore_main_fd_handler_active_set(hdl, ECORE_FD_READ);
 
         if ((ret < 0) && (code != EAGAIN)) goto err;