This small patch replaces unspec opcode with bitreverse in
riscv_brev8_<mode> insn.

gcc/ChangeLog:
        * config/riscv/crypto.md (UNSPEC_BREV8): Remov.
        (riscv_brev8_<mode>): Use bitreverse opcode.


-- 
With the best regards
Jivan Hakobyan