audio_processing/aec: NEON code should not be invoked if it is detectable, but is not NEON

There exist devices with runtime checks for NEON, but where the device is not NEON. One such device is Tegra2 on which currently NEON code is running.

This fix adds a missing feature check when initializing the AEC.

BUG=4304
R=kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42159004

Cr-Commit-Position: refs/heads/master@{#8559}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8559 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed