The function m_can_config_endisable() is not used outside of the m_can driver,
so mark it as static.

Link: https://lore.kernel.org/r/20201212175518.139651-5-mkl@pengutronix.deReviewed-by: Sean Nyekjaer <sean@geanix.com>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>