erasure-code: deactivate SSE optimizations

Workaround until the bug is diagnosed and fixed

http://tracker.ceph.com/issues/7826 refs #7826

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #1524 from dachary/wip-sse

erasure-code: deactivate SSE optimizations