vaapidecode: compilation fix
vaapidecode: compilation fix

gst_vaapi_decoder_state_changed() returns void. This patch fixes the
compilation where the toolchain uses restrictive flags as clang.

Signed-off-by: Víctor Manuel Jáquez Leal <4955886a7d0bd82ff6afce9ed1e93fbb85ab8088@intel.com>

gbeauchesne/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi