Fix derp return type in set_enable_async_thread_frame_context.

vulkan/device.cpp

@@ -2565,7 +2565,7 @@ void Device::promote_read_write_caches_to_read_only()
 	}
 }
 
-bool Device::set_enable_async_thread_frame_context(bool enable)
+void Device::set_enable_async_thread_frame_context(bool enable)
 {
 	LOCK();
 	lock.async_frame_context = enable;

vulkan/device.hpp

@@ -255,7 +255,7 @@ class Device
 	// but in the case where async threads are continuously pumping Vulkan work
 	// in the background, they need to reclaim memory if WSI goes to sleep for a long period of time.
 	void next_frame_context_in_async_thread();
-	bool set_enable_async_thread_frame_context(bool enable);
+	void set_enable_async_thread_frame_context(bool enable);
 
 	void wait_idle();
 	void end_frame_context();