target/riscv: Implement kvm_arch_get_registers

target/riscv: Implement kvm_arch_get_registers

Get GPR CSR and FP registers from kvm by KVM_GET_ONE_REG ioctl.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Mingwang Li <limingwang@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Message-id: 20220112081329.1835-5-jiangyifei@huawei.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>