target/arm: Convert Neon VSRA, VSRI, VRSHR, VRSRA 2-reg-shift insns to decodetree

target/arm: Convert Neon VSRA, VSRI, VRSHR, VRSRA 2-reg-shift insns to decodetree

Convert the VSRA, VSRI, VRSHR, VRSRA 2-reg-shift insns to decodetree.
(These are the last instructions in the group that are vectorized;
the rest all require looping over each element.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200522145520.6778-4-peter.maydell@linaro.org