src: shared: misc: add missing includes to header

Needed for clang-tidy prep work, as it requires headers to work standalone
(which is useful anyway).

src/shared/misc.h

@@ -27,6 +27,7 @@
 #include <unistd.h>
 
 #include "helpers.h"
+#include "rc.h"
 
 #define RC_LEVEL_BOOT           "boot"
 #define RC_LEVEL_DEFAULT        "default"