dt-bindings: can: rockchip_canfd: add rockchip CAN-FD controller

Add documentation for the rockchip rk3568 CAN-FD controller.

Co-developed-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Tested-by: Alibek Omarov <a1ba.omarov@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240904-rockchip-canfd-v5-1-8ae22bcb27cc@pengutronix.de


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>