[cpu] remove assert for recursion for #8475

Signed-off-by: Shell <smokewood@qq.com>

src/cpu.c

@@ -136,7 +136,6 @@ RTM_EXPORT(rt_spin_unlock_irqrestore)
  */
 struct rt_cpu *rt_cpu_self(void)
 {
-    RT_ASSERT(!rt_scheduler_is_available());
     return &_cpus[rt_hw_cpu_id()];
 }