lib: decoder: vp9: Set chroma_type by VP9 bit_depth
lib: decoder: vp9: Set chroma_type by VP9 bit_depth

The decoder's surface chroma type should depend on the bit depth
of VP9's parser. For 10bits VP9 stream, we need to use P10LE kind
10 bits surface as the decoder result.

Fixes #155

ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi