Clean up header includes

- Remove <errno.h> because related functions are in util.c now
 - Remove corresponding <string.h> if not used otherwise

components/kernel_release.c

@@ -1,8 +1,6 @@
 /* See LICENSE file for copyright and license details. */
-#include <errno.h>
 #include <sys/utsname.h>
 #include <stdio.h>
-#include <string.h>
 
 #include "../util.h"