motion-test: force C functions for the reference C context

It was instead using the highest available asm functions, which completely
kills the point of being a reference C context.
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/motion-test.c

@@ -128,6 +128,7 @@ int main(int argc, char **argv)
 
     ctx = avcodec_alloc_context3(NULL);
     ctx->flags |= CODEC_FLAG_BITEXACT;
+    av_force_cpu_flags(0);
     memset(&cctx, 0, sizeof(cctx));
     ff_dsputil_init(&cctx, ctx);
     for (c = 0; c < flags_size; c++) {