fft: mark xmm registers as clobbered in ff_imdct_calc_sse

Originally committed as revision 25363 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/x86/fft_sse.c

@@ -97,6 +97,7 @@ void ff_imdct_calc_sse(FFTContext *s, FFTSample *output, const FFTSample *input)
         :"+r"(j), "+r"(k)
         :"r"(output+n4), "r"(output+n4*3),
          "m"(*m1m1m1m1)
+        XMM_CLOBBERS_ONLY("%xmm0", "%xmm1", "%xmm7")
     );
 }