vpshufb is used to reverse R and B channels;
Code is otherwise the same as ARGBToAR30.

Bug: libyuv:751
Test: ABGRToAR30 unittest
Change-Id: I30e02925f5c729e4496c5963ba4ba4af16633b3b
Reviewed-on: https://chromium-review.googlesource.com/891807
Commit-Queue: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: richard winterton <rrwinterton@gmail.com>