media: v4l: vsp1: Replace manual DRM pipeline input setup in vsp1_du_setup_lif

The vsp1_du_setup_lif() function sets up the DRM pipeline input
manually. This duplicates the code from the
vsp1_du_pipeline_setup_inputs() function. Replace the manual
implementation by a call to the function.

As the pipeline has no enabled input in vsp1_du_setup_lif(), the
vsp1_du_pipeline_setup_inputs() function will not setup any RPF, and
will thus not setup formats on the BRU sink pads. This isn't a problem
as all inputs are disabled, and the BRU sink pads will be reconfigured
from the atomic commit handler when inputs will be enabled.

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>