drm: xlnx: zynqmp_dpsub: Pass format info to zynqmp_disp_layer_set_format()

The zynqmp_disp_layer_set_format() function only needs format
information, not a full plane state. Get the necessary info from the
plane state in the caller and pass it to zynqmp_disp_layer_set_format().
This prepares for calling the function from non-DRM code. This doesn't
introduce any functional change.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>