In preparation for RV128, consider more than just "w" for
operand size modification.  This will be used for the "d"
insns from RV128 as well.

Rename oper_len to get_olen to better match get_xlen.

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: 20211020031709.359469-10-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>