Refine current-task check in mo_task_suspend()

The previous implementation compared `kcb->task_current` against the
task's list node. This is always equivalent to comparing the task's TCB
in the current implementation, so no functional behavior is affected and
the mismatch can never occur.

This change simply makes the intended semantics explicit by comparing
against the TCB directly, improving readability and clarifying the
abstraction.

Author: vicLin8712

kernel/task.c

@@ -883,7 +883,7 @@ int32_t mo_task_suspend(uint16_t id)
     }
 
     task->state = TASK_SUSPENDED;
-    bool is_current = (kcb->task_current == node);
+    bool is_current = (kcb->task_current->data == task);
 
     CRITICAL_LEAVE();