omx: log OMX events with OMX_PERFORMANCE debug category
omx: log OMX events with OMX_PERFORMANCE debug category

It has been useful to have a clear raw and structured view of the gst
<-> OMX exchanges when debugging.

https://bugzilla.gnome.org/show_bug.cgi?id=797171

GStreamer/gst-omx,GStreamer/gst-omx,GStreamer/gst-omx