target/riscv: Introduce privilege version field in the CSR ops.

target/riscv: Introduce privilege version field in the CSR ops.

To allow/disallow the CSR access based on the privilege spec, a new field
in the csr_ops is introduced. It also adds the privileged specification
version (v1.12) for the CSRs introduced in the v1.12. This includes the
new ratified extensions such as Vector, Hypervisor and secconfig CSR.
However, it doesn't enforce the privilege version in this commit.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Message-Id: <20220303185440.512391-4-atishp@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>