Implement FCVTN (narrowing fp-to-fp conversions) from the SIMD
2-reg-misc category.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Message-id: 1394822294-14837-11-git-send-email-peter.maydell@linaro.org