Refactor of USB code within split_common (#11890)

* Initial refactor of usb code within split_common

* Add headers

* Correct disable condition

* Format

* Align func name

tmk_core/common/usb_util.c

@@ -0,0 +1,29 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "usb_util.h"
+#include "wait.h"
+
+__attribute__((weak)) void usb_disable(void) {}
+__attribute__((weak)) bool usb_connected_state(void) { return true; }
+__attribute__((weak)) bool usb_vbus_state(void) {
+#ifdef USB_VBUS_PIN
+    setPinInput(USB_VBUS_PIN);
+    wait_us(5);
+    return readPin(USB_VBUS_PIN);
+#else
+    return true;
+#endif
+}