target/arm: Implement fp16 for Neon pairwise fp ops

target/arm: Implement fp16 for Neon pairwise fp ops

Convert the Neon pairwise fp ops to use a single gvic-style
helper to do the full operation instead of one helper call
for each 32-bit part. This allows us to use the same
framework to implement the fp16.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200828183354.27913-36-peter.maydell@linaro.org