disas/riscv: Split out riscv-op.c.inc

Move rvi_opcode_data to riscv-op.c.inc and massage the lines into
OP() form.  Unlike other files, keep the enumeration and the table
intact for now, but build them both from the same source.

Adjust the names of rv_*mop to include _op_ to match the general pattern.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260812223142.349142-46-richard.henderson@linaro.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>