py/scheduler: Use MP_REGISTER_ROOT_POINTER().

This uses MP_REGISTER_ROOT_POINTER() to register sched_queue
instead of using a conditional inside of mp_state_vm_t.

Signed-off-by: David Lechner <david@pybricks.com>

py/mpstate.h

@@ -150,10 +150,6 @@ typedef struct _mp_state_vm_t {
     // dictionary with loaded modules (may be exposed as sys.modules)
     mp_obj_dict_t mp_loaded_modules_dict;
 
-    #if MICROPY_ENABLE_SCHEDULER
-    mp_sched_item_t sched_queue[MICROPY_SCHEDULER_DEPTH];
-    #endif
-
     // dictionary for the __main__ module
     mp_obj_dict_t dict_main;
 

py/scheduler.c

@@ -196,6 +196,8 @@ bool mp_sched_schedule_node(mp_sched_node_t *node, mp_sched_callback_t callback)
 }
 #endif
 
+MP_REGISTER_ROOT_POINTER(mp_sched_item_t sched_queue[MICROPY_SCHEDULER_DEPTH]);
+
 #endif // MICROPY_ENABLE_SCHEDULER
 
 // Called periodically from the VM or from "waiting" code (e.g. sleep) to