vapostproc: Build classification dynamically.
By default, the classification is "Converter/Filter/Colorspace/Scaler/Video/Hardware", but if VA post-processor driver supports either color balance, skin tone enhancement, sharpening or noise reduction, "Effect" is added.
Thus, if vapostproc ranking is raised, it can be chosen by autovideosink.
Cc: @thiblahute, @philn