drm: xlnx: zynqmp_dpsub: Set layer mode during creation

Set layer mode of operation (live or dma-based) during layer creation.

Each DPSUB layer mode of operation is defined by corresponding DT node port
connection, so it is possible to assign it during layer object creation.
Previously it was set in layer enable functions, although it is too late
as setting layer format depends on layer mode, and should be done before
given layer enabled.

Signed-off-by: Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkainen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240416-dp-live-fmt-v4-1-c7f379b7168e@amd.com