target/arm: Use FZ not FZ16 for SVE FCVT single-half and double-half

target/arm: Use FZ not FZ16 for SVE FCVT single-half and double-half

We were using the wrong flush-to-zero bit for the non-half input.

Fixes: 46d33d1e3c9
Cc: qemu-stable@nongnu.org (3.0.1)
Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-id: 20180810193129.1556-5-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>