[libcpu/arm64] add C11 atomic ticket spinlock (#8882)

* [libcpu/arm64] add C11 atomic ticket spinlock

Replace the former implementation of flag-based spinlock which is unfair

Besides, C11 atomic implementation is more readable (it's C anyway),
and maintainable. Cause toolchain can use their builtin optimization and
tune for different micro-architectures. For example armv8.5 introduces a
better instruction. The compiler can help with that when it knows your
target platform in support of it.

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

* fixup: RT_CPUS_NR

---------

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

src/cpu_mp.c

@@ -146,7 +146,7 @@ rt_base_t rt_cpus_lock(void)
     pcpu = rt_cpu_self();
     if (pcpu->current_thread != RT_NULL)
     {
-        register rt_ubase_t lock_nest = rt_atomic_load(&(pcpu->current_thread->cpus_lock_nest));
+        rt_ubase_t lock_nest = rt_atomic_load(&(pcpu->current_thread->cpus_lock_nest));
 
         rt_atomic_add(&(pcpu->current_thread->cpus_lock_nest), 1);
         if (lock_nest == 0)

src/scheduler_mp.c

@@ -1089,6 +1089,7 @@ void rt_exit_critical_safe(rt_base_t critical_level)
 
 void rt_exit_critical_safe(rt_base_t critical_level)
 {
+    RT_UNUSED(critical_level);
     return rt_exit_critical();
 }
 

src/thread.c

@@ -363,7 +363,8 @@ rt_thread_t rt_thread_self(void)
     self = rt_cpu_self()->current_thread;
     rt_hw_local_irq_enable(lock);
     return self;
-#else
+
+#else /* !RT_USING_SMP */
     extern rt_thread_t rt_current_thread;
 
     return rt_current_thread;