stream: Preserve enum class type in GetState()

Preserves the meaning/type-safetiness of the stream state instead of
making it an opaque u32. This makes it usable for other things outside
of the service HLE context.

src/core/hle/service/audio/audren_u.cpp

@@ -65,7 +65,7 @@ private:
     void GetAudioRendererState(Kernel::HLERequestContext& ctx) {
         IPC::ResponseBuilder rb{ctx, 3};
         rb.Push(RESULT_SUCCESS);
-        rb.Push<u32>(renderer->GetState());
+        rb.Push<u32>(static_cast<u32>(renderer->GetStreamState()));
         LOG_DEBUG(Service_Audio, "called");
     }