dt-bindings: arm: renesas: Document more R-Car Gen3e Socs and boards

Document the compatible values for the remaining R-Car Gen3e SoCs: R-Car
H3e (R8A779M0), M3e (R8A779M2), M3Ne (R8A779M4), M3Ne-2G (R8A779M5), E3e
(R8A779M6), D3e (R8A779M7), and H3Ne (R8A779M8).  These are different
gradings of R-Car Gen3 SoCs.

All R-Car Gen3e on-SoC devices are identical to the devices on the
corresponding R-Car Gen3 SoCs, and thus just use the compatible values
for the latter.  The root compatible properties do gain an additional
value, to sort out integration issues if they ever arise.

Document the use of these SoCs on the Salvator-XS, ULCB (with and
without Kingfisher extension), Ebisu, and Draak development boards.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/55271d405112f327753945072cde5d158ab815b1.1628766192.git.geert+renesas@glider.be