Temporarily disable scheduling class support

kernel/src/sched/mod.rs

@@ -9,6 +9,8 @@ mod stats;
 // Export the stats getter functions.
 pub use stats::{loadavg, nr_queued_and_running};
 
+// TODO: Use `sched_class::init` instead after the completion of #1676.
+pub use self::priority_scheduler::init;
 // There may be multiple scheduling policies in the system,
 // and subsequent schedulers can be placed under this module.
-pub use self::sched_class::{init, SchedAttr};
+pub use self::sched_class::SchedAttr;