Write VP9E_SET_TUNE_CONTENT to the correct location.

Change-Id: Ie8c976ececc79fd58c6eb16b7add053dc58e3bb8

vp9/vp9_cx_iface.c

@@ -1220,7 +1220,7 @@ static vpx_codec_err_t ctrl_set_svc_parameters(vpx_codec_alg_priv_t *ctx,
 static vpx_codec_err_t ctrl_set_tune_content(vpx_codec_alg_priv_t *ctx,
                                              va_list args) {
   struct vp9_extracfg extra_cfg = ctx->extra_cfg;
-  ctx->extra_cfg.content = CAST(VP9E_SET_TUNE_CONTENT, args);
+  extra_cfg.content = CAST(VP9E_SET_TUNE_CONTENT, args);
   return update_extra_cfg(ctx, &extra_cfg);
 }