Fifo: Make g_bSkipCurrentFrame a TU-local variable

This is only ever queried, making it a global isn't necessary.

Source/Core/VideoCommon/Fifo.cpp

@@ -33,7 +33,7 @@ namespace Fifo
 
 static constexpr u32 FIFO_SIZE = 2 * 1024 * 1024;
 
-bool g_bSkipCurrentFrame = false;
+static bool s_skip_current_frame = false;
 
 static Common::BlockingLoop s_gpu_mainloop;
 
@@ -82,7 +82,8 @@ void DoState(PointerWrap &p)
 		// We're good and paused, right?
 		s_video_buffer_seen_ptr = s_video_buffer_pp_read_ptr = s_video_buffer_read_ptr;
 	}
-	p.Do(g_bSkipCurrentFrame);
+
+	p.Do(s_skip_current_frame);
 	p.Do(s_last_sync_gpu_tick);
 }
 
@@ -129,7 +130,12 @@ void Shutdown()
 
 void SetRendering(bool enabled)
 {
-	g_bSkipCurrentFrame = !enabled;
+	s_skip_current_frame = !enabled;
+}
+
+bool WillSkipCurrentFrame()
+{
+	return s_skip_current_frame;
 }
 
 // May be executed from any thread, even the graphics thread.