directsoundsink: really use local ringbuffer spec helper var and init it a bit more
directsoundsink: really use local ringbuffer spec helper var and init it a bit more

from gst-plugins-base:3e750315e4d8c045b641222e147c62fe11ec6a78

freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good