media: v4l: vsp1: Don't start/stop media pipeline for DRM

The DRM support code manages a pipeline of VSP entities, each backed by
a media entity. When starting or stopping the pipeline, it starts and
stops the media pipeline through the media API in order to store the
pipeline pointer in every entity.

The driver doesn't use the pipe pointer in media entities, neither does
it rely on the other effects of the media_pipeline_start() and
media_pipeline_stop() functions. Furthermore, as the media links for the
DRM pipeline are never set up correctly, and as the pipeline can be
modified dynamically when enabling or disabling planes, the current
implementation is not correct. Remove the incorrect and unneeded code.

While at it remove the outdated comment that states that entities are
not started when the LIF is setup, as they now are.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>