can: mcp251xfd: ring: add support for runtime configurable RX/TX ring parameters

This patch adds runtime configurable RX and TX ring parameters via
ethtool to the driver.

Link: https://lore.kernel.org/20220313083640.501791-8-mkl@pengutronix.de


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