libs: decoder: h264: push frames as soon as possible
libs: decoder: h264: push frames as soon as possible

Push frames downstream as soon as possible instead of waiting until
they are ejected from the DPB.

This patch makes the decoder not comply with the H.264 specification,
but it is required for some video cameras.

https://bugzilla.gnome.org/show_bug.cgi?id=762509

Signed-off-by: Víctor Manuel Jáquez Leal <853e0dbb5ddd43a0f0483f24794ae05c4c52af91@igalia.com>

ceyusa/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi