[docs][RISCV] List Zcmp and Zicbop as "Supported" rather than "Assembly support (#68717)

Zcmp codegen is implemented (see RISCVMoveMerger and
RISCVPushPopOptimizer), while Zicbop instructions are selected for
llvm.prefetch instrinsics. So I believe it's correct to mark both as
"Supported" and this is just an oversight.