OMAP DSS warning in apply.c

kautobuildv2 discovered this in its omap4430sdp oldconfig build:

drivers/video/omap2/dss/apply.c:350: warning: 'wait_pending_extra_info_updates' defined but not used

This looks like a valid warning, because wait_pending_extra_info_updates()
seems to be completely unreferenced.  Should the function be removed?
It looks like extra_updated_completion can also be removed as well, as
that function is the only place it gets initialized and waited for.

The function also looks weird - it calls extra_info_update_ongoing() first
under a lock, and then outside the lock.  It's not particularly nice API
wise to have stuff sometimes called under a lock and sometimes not.