media: v4l: vsp1: Move DRM pipeline output setup code to a function

In order to make the vsp1_du_setup_lif() easier to read, and for
symmetry with the DRM pipeline input setup, move the pipeline output
setup code to a separate function.

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>