Add Display SubSystem (DSS) DT node for the AM625 SoC.

The DSS supports one each of video pipeline (vid) and video-lite
pipeline (vidl1). It outputs OLDI signals on one video port (VP1) and
DPI signals on another (VP2). The video ports are connected to the
pipelines via 2 identical overlay managers (ovr1 and ovr2).

Also add the DT node for DSS clock divider. This is a fixed-factor-clock
and does not have any register. This comes into effect whenenver OLDI
display is used. The input to this divider is a serial clock used by
OLDI TXes. The divider divides the input clock by 7, and provides the
pixel clock to VP1.
Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Link: https://lore.kernel.org/r/20230809084559.17322-3-a-bhatia1@ti.comSigned-off-by: Nishanth Menon <nm@ti.com>