Further SSE2 optimizations for the AEC3 adaptive filter.

This CL adds further SSE2 optimizations for the AEC3
adaptive filter.

The changes are bitexact

BUG=webrtc:6018

Review-Url: https://codereview.webrtc.org/2810133002
Cr-Original-Commit-Position: refs/heads/master@{#17667}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 69ffdf49382cda8ae4baa7173ab5237cb815292a