core_timing: Make use of uintptr_t to represent user_data

Makes the interface future-proofed for supporting other platforms in the event we ever support platforms with differing pointer sizes. This way, we have a type in place that is always guaranteed to be able to represent a pointer exactly.

src/core/memory/cheat_engine.h

@@ -72,7 +72,7 @@ public:
     void Reload(std::vector<CheatEntry> cheats);
 
 private:
-    void FrameCallback(u64 userdata, std::chrono::nanoseconds ns_late);
+    void FrameCallback(std::uintptr_t user_data, std::chrono::nanoseconds ns_late);
 
     DmntCheatVm vm;
     CheatProcessMetadata metadata;