shared: move cg_set_access() declaration to right header file

This function was moved from cgroup-util.c to cgroup-setup.c a while
back, but the prototype in the matching header files wasn't migrated.
Let's fix that.

src/core/scope.c

@@ -4,6 +4,7 @@
 #include <unistd.h>
 
 #include "alloc-util.h"
+#include "cgroup-setup.h"
 #include "dbus-scope.h"
 #include "dbus-unit.h"
 #include "exit-status.h"