v4l2: videoencoder: Adding propose_allocation method
v4l2: videoencoder: Adding propose_allocation method

Signed-off-by: Pablo Anton <5ba87db0255dba28a3a094ad071ca6f87047f505@vodalys-labs.com>

veo-labs/gst-plugins-good,veo-labs/gst-plugins-good,veo-labs/gst-plugins-good,veo-labs/gst-plugins-good