avcodec/vp8: Remove always-false check

Since e9b6617579 a codec's close
function is never ever called for a codec whose init function has not
been called; in particular, it is never ever called if the
AVCodecContext's private data has not been allocated.

Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/vp8.c

@@ -2826,9 +2826,6 @@ av_cold int ff_vp8_decode_free(AVCodecContext *avctx)
     VP8Context *s = avctx->priv_data;
     int i;
 
-    if (!s)
-        return 0;
-
     vp8_decode_flush_impl(avctx, 1);
     for (i = 0; i < FF_ARRAY_ELEMS(s->frames); i++)
         av_frame_free(&s->frames[i].tf.f);