target/riscv: Use gen_unary_per_ol for RVB

target/riscv: Use gen_unary_per_ol for RVB

The count zeros instructions require a separate implementation
for RV32 when TARGET_LONG_BITS == 64.

Reviewed-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20211020031709.359469-13-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>