重写SMP模块 (#633)

* 修复cpumask的迭代器的错误。

* 能进系统（AP核心还没有初始化自身）

* 初始化ap core

* 修改percpu

* 删除无用的cpu.c

* riscv64编译通过

kernel/src/driver/keyboard/ps2_keyboard.rs

@@ -181,7 +181,7 @@ impl IrqHandler for Ps2KeyboardIrqHandler {
         let status = unsafe { CurrentPortIOArch::in8(PORT_PS2_KEYBOARD_STATUS.into()) };
         let status = Ps2StatusRegister::from(status);
         if !status.outbuf_full() {
-            return Ok(IrqReturn::NotHandled);
+            return Ok(IrqReturn::Handled);
         }
 
         let input = unsafe { CurrentPortIOArch::in8(PORT_PS2_KEYBOARD_DATA.into()) };