Reoptimizes the 8-tap smooth filter.

Results:
derf: +0.101%
yt: +0.157%
hd: +0.791%
stdhd: +0.264%

The next step will be to reoptimize the other two filters.

Change-Id: I3d256a510ad9c7c30c33fae4a70fb43dfc708ed0