dt-bindings: can: rcar_can: document r8a77965 support

Document the support for rcar_can on R8A77965 SoC devices.
Add R8A77965 to the list of SoCs which require the "assigned-clocks" and
"assigned-clock-rates" properties (thanks, Sergei).

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>