target/riscv: Remove the hardcoded SSTATUS_SD macro

This also ensures that the SD bit is not writable.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Message-id: 9ea842309f0fd7adff172790f5b5fc058b40f2f1.1619234854.git.alistair.francis@wdc.com
2 files changed