[media] v4l: vsp1: video: Reorder functions

Move the pipeline initialization and cleanup functions to prepare for
the next commit. No functional code change is performed here.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>