avcodec/h263dec: fix "incompatible pointer type" warning

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h263dec.c

@@ -569,7 +569,7 @@ retry:
         ff_thread_finish_setup(avctx);
 
     if (CONFIG_MPEG4_VDPAU_DECODER && (s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU)) {
-        ff_vdpau_mpeg4_decode_picture(s, s->gb.buffer, s->gb.buffer_end - s->gb.buffer);
+        ff_vdpau_mpeg4_decode_picture(avctx->priv_data, s->gb.buffer, s->gb.buffer_end - s->gb.buffer);
         goto frame_end;
     }