Mark ff_fft_end av_cold.

Originally committed as revision 16851 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/fft.c

@@ -206,7 +206,7 @@ void ff_fft_permute_c(FFTContext *s, FFTComplex *z)
     }
 }
 
-void ff_fft_end(FFTContext *s)
+av_cold void ff_fft_end(FFTContext *s)
 {
     av_freep(&s->revtab);
     av_freep(&s->exptab);