reboot-util: merge with raw-reboot.h

The header raw-reboot.h is only used with reboot-util. Let's merge them.

src/basic/raw-reboot.h

@@ -1,15 +0,0 @@
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-#pragma once
-
-#include <linux/reboot.h>
-#include <sys/reboot.h>
-#include <sys/syscall.h>
-#include <unistd.h>
-
-/* glibc defines the reboot() API call, which is a wrapper around the system call of the same name, but without the
- * extra "arg" parameter. Since we need that parameter for some calls, let's add a "raw" wrapper that is defined the
- * same way, except it takes the additional argument. */
-
-static inline int raw_reboot(int cmd, const void *arg) {
-        return (int) syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, arg);
-}