Revert of Properly enable S32_D16_filter_DX_SSE2 optimization.

Revert of Properly enable S32_D16_filter_DX_SSE2 optimization. (https://codereview.chromium.org/239453010/)

Reason for revert:
Broke GMs in 565 mode. To repro:
out/Debug/gm --match filterbitmap_image_mandrill -w . --config 565
open filterbitmap_image_mandrill_512.png_565.png

Original issue's description:
> Properly enable S32_D16_filter_DX_SSE2 optimization.
> 
> Currently, the S32_D16_filter_DX_SSE2 optimization is only used in
> configurations where the maximum SSE level is SSE2.
> This patch enables it for higher levels, as well.
> Also, refactored the function a bit, to make future modifications
> less error-prone.
> 
> Author: henrik.smiding@intel.com
> 
> Signed-off-by: Henrik Smiding <henrik.smiding@intel.com>;
> 
> Committed: http://code.google.com/p/skia/source/detail?r=14333

TBR=reed@google.com,mtklein@google.com,tomhudson@google.com,djsollen@google.com,joakim.landberg@intel.com,henrik.smiding@intel.com
NOTREECHECKS=true
NOTRY=true

Committed: http://code.google.com/p/skia/source/detail?r=14336

[bsalomon, 2014-04-23 20:07:00]

Created Revert of Properly enable S32_D16_filter_DX_SSE2 optimization.

[commit-bot: I haz the power, 2014-04-23 20:07:14]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/bsalomon@google.com/246393013/1

[commit-bot: I haz the power, 2014-04-23 20:07:20]

Change committed as 14336