Fix up splittest/bluepill (#17897)

keyboards/handwired/splittest/keymaps/serial_fullduplex/config.h

@@ -3,6 +3,4 @@
 
 #pragma once
 
-#include "config_common.h"
-
 #define SPLIT_SERIAL_FULLDUPLEX

keyboards/handwired/splittest/keymaps/serial_fullduplex/halconf.h

@@ -1,2 +1,8 @@
+// Copyright 2022 dvermd (@dvermd)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
 #define HAL_USE_SERIAL TRUE
+
 #include_next <halconf.h>

keyboards/handwired/splittest/keymaps/serial_fullduplex/keymap.c

@@ -1,3 +1,6 @@
+// Copyright 2022 dvermd (@dvermd)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 #include QMK_KEYBOARD_H
 
 const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {[0] = LAYOUT(KC_L, KC_R)};