can: mcp251xfd: Fix header block to clarify independence from OF

The driver is neither dependent on OF, nor it requires any OF headers.
Fix header block to clarify independence from OF.

Link: https://lore.kernel.org/r/http://lore.kernel.org/r/20210531084444.1785397-2-mkl@pengutronix.de


Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>