mpeg2dec: Avoid dropping first GOP
mpeg2dec: Avoid dropping first GOP

We use the mpeg2_fbuf_t id field as an integer and not as a pointer, so
do not check if it is NULL or not.

And cleanup a bit of debug

GStreamer/gst-plugins-ugly,krieger-od/gst-plugins-ugly,cablelabs/gst-plugins-ugly,cablelabs/gst-plugins-ugly,surround-io/gst-plugins-ugly,sebras/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,Distrotech/gst-plugins-ugly,surround-io/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,krieger-od/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,Lachann/gst-plugins-ugly,Distrotech/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,GStreamer/gst-plugins-ugly,collects/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,Lachann/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,Kurento/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,Distrotech/gst-plugins-ugly,collects/gst-plugins-ugly,GStreamer/gst-plugins-ugly,Distrotech/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,collects/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,cablelabs/gst-plugins-ugly,Distrotech/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,jar1karp/gst-plugins-ugly,krieger-od/gst-plugins-ugly,Kurento/gst-plugins-ugly,sebras/gst-plugins-ugly,Lachann/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,jar1karp/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,surround-io/gst-plugins-ugly,collects/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,jar1karp/gst-plugins-ugly,sebras/gst-plugins-ugly,Kurento/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,krieger-od/gst-plugins-ugly