X86 doesn't have detection routines so map to default FFT routines.

For X86, just #define the detection routines to the default
routines. This makes the API the same for x86 and arm.

BUG=
R=andrew@webrtc.org, xingnan.wang@chromium.org

Review URL: https://webrtc-codereview.appspot.com/4749004

git-svn-id: http://webrtc.googlecode.com/svn/deps/third_party/openmax@5205 4adac7df-926f-26a2-2b94-8c16560cd09d