avcodec/mpegvideo_enc: Clear mmx state in ff_mpv_reallocate_putbitbuffer()

This function must be called from the mb or slice encoding loop and MMX state may not
be clean there

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 03ec6b780c)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mpegvideo_enc.c

@@ -2912,6 +2912,8 @@ int ff_mpv_reallocate_putbitbuffer(MpegEncContext *s, size_t threshold, size_t s
             return AVERROR(ENOMEM);
         }
 
+        emms_c();
+
         av_fast_padded_malloc(&new_buffer, &new_buffer_size,
                               s->avctx->internal->byte_buffer_size + size_increase);
         if (!new_buffer)