core: remove reboot.h

with the new PM, the reboot.h is deprecated and pm_reboot() from
periph/pm.h should be used.

core/include/reboot.h

@@ -1,43 +0,0 @@
-/*
- * Copyright (C) 2016 Kaspar Schleiser <kaspar@schleiser.de>
- *
- * This file is subject to the terms and conditions of the GNU Lesser
- * General Public License v2.1. See the file LICENSE in the top level
- * directory for more details.
- */
-
-/**
- * @addtogroup  core_internal
- * @{
- *
- * @file
- * @brief       Reboot function
- *
- * @author      Kaspar Schleiser <kaspar@schleiser.de>
- */
-
-#ifndef REBOOT_H_
-#define REBOOT_H_
-
-#include "periph/pm.h"
-
-#ifdef __cplusplus
- extern "C" {
-#endif
-
-/**
- * @brief Immediately reboots the system.
- *
- * This function is used by core_panic() when the DEVELHELP macro is not defined.
- */
-static inline void reboot(void)
-{
-    pm_reboot();
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* REBOOT_H_ */
-/** @} */