log failing OMX calls as errors
log failing OMX calls as errors

I find it confusing when debugging that OMX calls returning an error
where not logged as GST_LEVEL_ERROR making them harder to spot.
Fix this by introducing simple log macros checking the return value of
the OMX call and logging failures as errors.

https://bugzilla.gnome.org/show_bug.cgi?id=791069

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