Bart: Instatiate lm_head once without wasting memory
Marking this down since I agreed to do it https://github.com/huggingface/transformers/pull/4803#discussion_r443381438

cc @patrickvonplaten 

this will happen as part of TPU issue.<|||||>Can you link the issue? Is there an open PR for this already? <|||||>This one: https://github.com/huggingface/transformers/pull/5960 , but it's broken afaict.<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
