can: flexcan: convert the driver to DT-only

The flexcan driver runs only on DT platforms, so simplify the code by using
of_device_get_match_data() to retrieve the driver data and also by removing the
unused id_table.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20201128132855.7724-1-festevam@gmail.com


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