gpu: Use std::stop_token in WaitFence for VSync thread

Fixes a hang that may occur when stopping emulation and the VSync thread is blocked on the syncpoint condition variable.

src/video_core/gpu.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <memory>
+#include <stop_token>
 
 #include "common/bit_field.h"
 #include "common/common_types.h"
@@ -209,7 +210,7 @@ public:
     [[nodiscard]] const VideoCore::ShaderNotify& ShaderNotify() const;
 
     /// Allows the CPU/NvFlinger to wait on the GPU before presenting a frame.
-    void WaitFence(u32 syncpoint_id, u32 value);
+    void WaitFence(u32 syncpoint_id, u32 value, std::stop_token stop_token = {});
 
     void IncrementSyncPoint(u32 syncpoint_id);