Workaround to fix failure of this pipeline:
gst-launch-1.0 videotestsrc ! video/x-raw, format=I420 ! waylandsink drm-device=/dev/dri/card0 ERROR: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: Video memory can not be written from userspace.
320x240 is aligned to 384x240 (size=138240 in I420) when allocating through DRM dumb allocator (STM dri card).
Patch consist to force GST_BUFFER_FLAG_TAG_MEMORY right before unref so that we don't fall into the resize case later on.
This is a workaround only, this needs a deeper analysis for a better patch...