dt-bindings: net: can: c_can: convert to json-schema

Convert the Bosch C_CAN/D_CAN controller device tree binding
documentation to json-schema.

Document missing properties.
Remove "ti,hwmods" as it is no longer used in TI dts.
Make "clocks" required as it is used in all dts.
Update the examples.

Link: https://lore.kernel.org/r/20210805192750.9051-1-dariobin@libero.it


Signed-off-by: Dario Binacchi <dariobin@libero.it>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>