target/arm: Convert Neon VQABS, VQNEG to decodetree

target/arm: Convert Neon VQABS, VQNEG to decodetree

Convert the Neon VQABS and VQNEG insns to decodetree.
Since these are the only ones which need cpu_env passing to
the helper, we wrap the helper rather than creating a whole
new do_2misc_env() function.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200616170844.13318-15-peter.maydell@linaro.org