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.