init: add an init_utimes helper

Add a simple helper to set timestamps with a kernel space file name and
switch the early init code over to it.

Signed-off-by: Christoph Hellwig <hch@lst.de>

init/initramfs.c

@@ -111,8 +111,7 @@ static long __init do_utime(char *filename, time64_t mtime)
 	t[0].tv_nsec = 0;
 	t[1].tv_sec = mtime;
 	t[1].tv_nsec = 0;
-
-	return do_utimes(AT_FDCWD, filename, t, AT_SYMLINK_NOFOLLOW);
+	return init_utimes(filename, t);
 }
 
 static __initdata LIST_HEAD(dir_list);