gpu_thread: Don't spin wait if there are no GPU commands.

src/video_core/gpu_thread.cpp

@@ -31,8 +31,7 @@ static void RunThread(VideoCore::RendererBase& renderer, Tegra::DmaPusher& dma_p
 
     CommandDataContainer next;
     while (state.is_running) {
-        while (!state.queue.Empty()) {
-            state.queue.Pop(next);
+        next = state.queue.PopWait();
         if (const auto submit_list = std::get_if<SubmitListCommand>(&next.data)) {
             dma_pusher.Push(std::move(submit_list->entries));
             dma_pusher.DispatchCalls();
@@ -49,7 +48,6 @@ static void RunThread(VideoCore::RendererBase& renderer, Tegra::DmaPusher& dma_p
         }
         state.signaled_fence.store(next.fence);
     }
-    }
 }
 
 ThreadManager::ThreadManager(Core::System& system) : system{system} {}