RISC-V: Add hypervisor extension related CSR defines

euleros inclusion
category: feature
feature: initial KVM RISC-V support
bugzilla: 46845
CVE: NA

This patch extends asm/csr.h by adding RISC-V hypervisor extension
related defines.

Reference: https://gitee.com/openeuler/kernel/issues/I26X9V


Signed-off-by: Anup Patel <anup.patel@wdc.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Yifei Jiang <jiangyifei@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>