kern: switch->nx, implement sleep manager init

libraries/libmesosphere/include/mesosphere/kern_k_target_system.hpp

@@ -15,11 +15,10 @@
  */
 #pragma once
 #include <mesosphere/kern_common.hpp>
+#include <mesosphere/kern_select_system_control.hpp>
 
 namespace ams::kern {
 
-    class KSystemControl;
-
     class KTargetSystem {
         private:
             friend class KSystemControl;