can: tcan4x5x: tcan4x5x_regmap: set reg_stride to 4

This patch sets the regmap stide to 4, as the chip only supports access on 32
bit alligned access.

Reviewed-by: Dan Murphy <dmurphy@ti.com>
Tested-by: Sean Nyekjaer <sean@geanix.com>
Link: https://lore.kernel.org/r/20201215231746.1132907-13-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>