Drivers may signal end of sequence using an empty buffer and LAST buffer set, or just an empty buffer on certain legacy implementation. When this occured, we'd send GST_V4L2_FLOW_LAST_BUFFER were the code expected GST_FLOW_EOS. Stop abusing GST_FLOW_EOS and port all the code to the new GST_V4L2_FLOW_LAST_BUFFER. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4669>