target/riscv: rvk: add support for sha512 related instructions for RV32 in zknh extension

target/riscv: rvk: add support for sha512 related instructions for RV32 in zknh extension

 - add sha512sum0r, sha512sig0l, sha512sum1r, sha512sig1l, sha512sig0h and sha512sig1h instructions

Co-authored-by: Zewen Ye <lustrew@foxmail.com>
Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220423023510.30794-10-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>