dt-bindings: soc: renesas: Document R-Car V4H White Hawk Single

Document the compatible values for the Renesas R-Car V4H ES2.0
(R8A779G2) SoC and the Renesas White Hawk Single board.
The former is an updated version of R-Car V4H (R8A779G0).
The latter is a single-board integration of the Renesas White Hawk CPU
and Breakout board stack.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/a44d990c962c8e0aac3b133eaa563f8c92b2ce29.1706192990.git.geert+renesas@glider.be