!449 LoongArch: add kvm support

Merge Pull Request from: @Hongchen_Zhang 
 
Added simulation of csr devices, interrupt controller devices, mmu, 
timers, etc. in kvm under loongarch structure.
kvm-based acceleration for qemu applications on 5000 servers or 5000 
desktops with loongarch cpu

Characteristic Details: 
1) cpu 
  - Support up to 64 vcpu, support vcpu hot-plug
2) memory
  - Back-end memory supports normal huge pages and transparent huge pages
  - Support balloon 
  - Support memory hot-swap
3) Peripherals
  - Support standard interfaces PCI, SATA, SCSI, USB, virtio devices
  - Support multiple NICs, multiple disks
  - Supports hot-plug of devices
4) boot
  - Support UEFI bios boot
  - Support boot order
  - Direct kernel boot support
  - Support tpm
5) Migration
  - Support for virtual machine snapshots
  - Support for virtual machine saving and recovery
  - Support for shared storage migration
  - Support for incremental migration
  - Supports full copy migration of storage

Test passed with below step:
1、Install virt-manager
2、Install libvirt
3、Install qemu
4、Download loongarch's qcow2 file
5、Create a virtual machine on virtu-manager using the qcow2 file
6、Start the virtual machine and find that the virtual machine can run normally 
 
Link:https://gitee.com/openeuler/kernel/pulls/449

 

Reviewed-by: Guo Dongtai <guodongtai@kylinos.cn>
Reviewed-by: Kevin Zhu <zhukeqian1@huawei.com>
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>