target/arm: Implement SVE2 saturating multiply-add high

SVE2 has two additional sizes of the operation and unlike NEON,
there is no saturation flag.  Create new entry points for SVE2
that do not set QC.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210525010358.152808-36-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>