arm64: dts: renesas: white-hawk: Add CSI/DSI sub-board

Add a DTS file for the R-Car V4H White Hawk CSI/DSI sub-board
(RTP8A779G0ASKB0SC0SA000), and include it from the main
r8a779g0-white-hawk.dts.

For now its contents are limited to the Board ID EEPROM.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/265f7782743c539c57906e8207785f8b0d80d5d0.1662715538.git.geert+renesas@glider.be