can: m_can: Limit coalescing to peripheral instances

The use of coalescing for non-peripheral chips in the current
implementation is limited to non-existing. Disable the possibility to
set coalescing through ethtool.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-8-msp@baylibre.com


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