video_core: Use adaptive mutex on Linux (#2105)

Fix performance regression with #1973 on SteamDeck

src/common/adaptive_mutex.h

@@ -0,0 +1,27 @@
+// SPDX-FileCopyrightText: Copyright 2024 shadPS4 Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#ifdef __linux__
+#include <pthread.h>
+#endif
+
+namespace Common {
+
+#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+class AdaptiveMutex {
+public:
+    void lock() {
+        pthread_mutex_lock(&mutex);
+    }
+    void unlock() {
+        pthread_mutex_unlock(&mutex);
+    }
+
+private:
+    pthread_mutex_t mutex = PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP;
+};
+#endif // PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+
+} // namespace Common