vaapipluginutil: add RGBA/BGRA to memory:VASurface caps features
vaapipluginutil: add RGBA/BGRA to memory:VASurface caps features

Useful for:
vaapipostproc ! video/x-raw(memory:VASurface, RGBA) ! vaapsink

CapOM/gstreamer-vaapi,CapOM/gstreamer-vaapi,CapOM/gstreamer-vaapi