dt-bindings: arm: renesas: Add R-Car M3-W+ ULCB with Kingfisher

Document the use of the Kingfisher expansion board with the R-Car
Starter Kit Pro equipped with an R-Car M3-W+ (aka M3-ES3.0) SoC.

Inspired from v5.5 commit 24169f0a ("dt-bindings: arm: renesas:
Add R-Car M3-N ULCB with Kingfisher").

Suggested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20201030083051.18752-4-erosca@de.adit-jv.com


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