target/riscv: Remove redundant insn length check for zama16b

target/riscv: Remove redundant insn length check for zama16b

Compressed encodings also applies to zama16b.
https://github.com/riscv/riscv-isa-manual/pull/1557

Suggested-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240802072417.659-2-zhiwei_liu@linux.alibaba.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>