dt-bindings: can: mcp251x: change example interrupt type to IRQ_TYPE_LEVEL_LOW

The MCP2515 datasheet clearly describes a level-triggered interrupt pin.
Change example bindings accordingly.

Link: https://lore.kernel.org/r/20200915223527.1417033-25-mkl@pengutronix.de


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