clk: renesas: r8a779g0: Add display related clocks

Add clocks related to display which are needed to get the DSI output
working.

Extracted from Renesas BSP tree.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20221201095631.89448-4-tomi.valkeinen+renesas@ideasonboard.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>