vsad16_mmx2 only applies if encoders are turned on

Originally committed as revision 2736 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/i386/dsputil_mmx.c

@@ -2158,7 +2158,9 @@ void dsputil_init_mmx(DSPContext* c, AVCodecContext *avctx)
                 c->put_no_rnd_pixels_tab[1][2] = put_no_rnd_pixels8_y2_mmx2;
                 c->avg_pixels_tab[0][3] = avg_pixels16_xy2_mmx2;
                 c->avg_pixels_tab[1][3] = avg_pixels8_xy2_mmx2;
+#ifdef CONFIG_ENCODERS
                 c->vsad[0] = vsad16_mmx2;
+#endif //CONFIG_ENCODERS
             }
 
 #if 1