When loading or storing the data, the unaligned address will greatly degrade
the optimization performance, so non-aligned access instructions are required
on the loongson platform.

Also delete the optimization function:ScaleARGBFilterCols_MMI,
because it degraded the performance.

BUG=libyuv:804
R=fbarchard@chromium.org

Change-Id: If4c15886a21cdcbac7ae8b336292e4549acf1e47
Reviewed-on: https://chromium-review.googlesource.com/1164627Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>