HW/SerialInterface: Refactor to class.

Source/Core/Core/HW/VideoInterface.cpp

@@ -885,8 +885,9 @@ void VideoInterfaceManager::Update(u64 ticks)
   {
     Core::UpdateInputGate(!Config::Get(Config::MAIN_INPUT_BACKGROUND_INPUT),
                           Config::Get(Config::MAIN_LOCK_CURSOR));
-    SerialInterface::UpdateDevices();
-    m_half_line_of_next_si_poll += 2 * SerialInterface::GetPollXLines();
+    auto& si = m_system.GetSerialInterface();
+    si.UpdateDevices();
+    m_half_line_of_next_si_poll += 2 * si.GetPollXLines();
   }
 
   // If this half-line is at the actual boundary of either field, schedule an SI poll to happen