* [rt-smart/mem] remove pv_offset

* [rt-smart] list kernel space command

* [rt-smart] restore ioremap region

* [revert] restore kernel space isolation

* [rt-smart/pv_off] code format

* [rt-smart] add get_pvoff()

* [pvoffset] pvoff as constant for C codes

* [pvoff] pvoff as interfaces

synchronize virtual memory system works.
adding kernel virtual memory management layer for page-based MMU enabled architecture
porting libcpu MMU codes
porting lwp memory related codes

* [dfs] sync cromfs

* [rt-smart]Weaken RT_USING_LWP, use RT_USING_SMART as macro configuration

* [format] fix some format issue.

* Synchronize the code of the rt mart branch to the master branch.
  * TTY device
  * Add lwP code from rt-smart
  * Add vnode in DFS, but DFS will be re-write for rt-smart
  * There are three libcpu for rt-smart:
    * arm/cortex-a, arm/aarch64
    * riscv64
Co-authored-by: NRbb666 <zhangbingru@rt-thread.com>
Co-authored-by: Nzhkag <zhkag@foxmail.com>

If the application defines dozens of global variables,
the speed of clearing the bss segment will be slower.

Because icache can be enabled before the mmu enabled.
Therefore, in order to speed up the process of clearing the BSS segment,
enable icache needs to be put ahead.

[update] Removed C++ global constructor initialization, this method is not used in GCC4.7 and later versions.

1. 去除start_gcc.s中set_secondary_cpu_boot_address代码，这部分提取到qemu-vexpress-a9 bsp中。
2. 移动cpu.c中rt_hw_cpu_id函数到cp15_gcc.s，使用汇编实现，采用wake属性，方便bsp根据cpu特性获取CPU ID（多cpu集群中，不同厂家使用组合不一样）.
3. 整理start_gcc.s 适应多核启动，原来的代码只考虑到双核的情况。