avfilter/af_amultiply: Remove unnecessary emms_c()

The floating point dsp code does not use MMX registers
since 2718a3be1f.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/af_amultiply.c

@@ -90,7 +90,6 @@ static int activate(AVFilterContext *ctx)
                                      plane_samples);
             }
         }
-        emms_c();
 
         av_frame_free(&s->frames[0]);
         av_frame_free(&s->frames[1]);