Input: drop vb2_ops_wait_prepare/finish

Input: drop vb2_ops_wait_prepare/finish

Since commit 88785982a19d ("media: vb2: use lock if wait_prepare/finish
are NULL") it is no longer needed to set the wait_prepare/finish
vb2_ops callbacks as long as the lock field in vb2_queue is set.

Since the vb2_ops_wait_prepare/finish callbacks already rely on that field,
we can safely drop these callbacks.

This simplifies the code and this is a step towards the goal of deleting
these callbacks.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Link: https://lore.kernel.org/r/ec811552-6014-43d4-9fcc-2ac729a8b08e@xs4all.nl
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>