aarch64.risu: complete C3.6.17 AdvSIMD two-reg misc
aarch64.risu: complete C3.6.17 AdvSIMD two-reg misc

Signed-off-by: Alex Bennée <97ce1413105b2e68f811413f1ea07a68d9e5b40a@linaro.org>

vivier/risu,stsquad/risu,stsquad/risu,stsquad/risu,vivier/risu