target/riscv: Define macros and variables for ss1p13

target/riscv: Define macros and variables for ss1p13

Add macros and variables for RISC-V privilege 1.13 support.

Signed-off-by: Fea.Wang <fea.wang@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Weiwei Li <liwei1518@gmail.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240606135454.119186-3-fea.wang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>