don't read CSR in csrrw(i) with rd=0#1628

ShengMingTangAndes wants to merge 1 commit intoriscv-software-src:masterriscv-software-src/riscv-isa-sim:masterfrom

ShengMingTangAndes:csrrw-rd0-readShengMingTangAndes/riscv-isa-sim:csrrw-rd0-readCopy head branch name to clipboard