fix: moved attach serial down

To avoid WASM serialization issues.

src/gb.rs

@@ -358,10 +358,6 @@ impl GameBoy {
         self.apu().set_clock_freq(value);
     }
 
-    pub fn attach_serial(&mut self, device: Box<dyn SerialDevice>) {
-        self.serial().set_device(device);
-    }
-
     pub fn attach_stdout_serial(&mut self) {
         self.attach_serial(Box::<StdoutDevice>::default());
     }
@@ -463,6 +459,10 @@ impl GameBoy {
         let data = read_file(path);
         self.load_rom(&data)
     }
+
+    pub fn attach_serial(&mut self, device: Box<dyn SerialDevice>) {
+        self.serial().set_device(device);
+    }
 }
 
 #[cfg(feature = "wasm")]