can: m_can: Implement BQL

Implement byte queue limiting in preparation for the use of xmit_more().

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240207093220.2681425-14-msp@baylibre.com


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