vaapivideobufferpool: share options flag with pluginbase
Originally, vaapivideobufferpool has a set of boolean variables for the buffer configuration options. This pach changes these boolean variables for a single bitwise, just as it is used in pluginbase. Hence, the internal enum was moved to vaapivideobufferpool header. https://bugzilla.gnome.org/show_bug.cgi?id=765435