media: vimc: stream: init/terminate the first entity

The s_stream callback was not being called for the first entity in the
stream pipeline array.
Instead of verifying the type of the node (video or subdevice) and
calling s_stream from the second entity in the pipeline, do this process
for all the entities in the pipeline for consistency.

The previous code was not a problem because the first entity is a video
device and not a subdevice, but this patch prepares vimc to allow
setting some configuration in the entity before calling s_stream.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Tested-by: André Almeida <andre.almeida@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: fix line-too-long warning]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>