media: vb2: vb2_core_queue_init(): sanity check lock and wait_prepare/finish

Add two new checks:

1) wait_prepare and wait_finish callbacks are either both present or
   both unset, you can't mix.
2) if lock == NULL, then wait_prepare (and due to check 1 also
   wait_finish) must be present.

These checks should prevent the case where lock == NULL, but there
is no way to release/reacquire whatever lock is used when waiting
for a buffer to arrive in VIDIOC_DQBUF.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>