SSE2 code for the filter in MFQE.

The SSE2 code is from VP8 MFQE, reuse it in VP9. No change on VP8
side. In our testing, we achieve 2X speed by adopting this change.

Change-Id: Ib2b14144ae57c892005c1c4b84e3379d02e56716
4 files changed