can: tcan4x5x: tcan4x5x_can_probe(): add missing error checking for devm_regmap_init()

This patch adds the missing error checking when initializing the regmap
interface fails.

Fixes: 5443c226 ("can: tcan4x5x: Add tcan4x5x driver to the kernel")
Cc: Dan Murphy <dmurphy@ti.com>
Link: http://lore.kernel.org/r/20201019154233.1262589-7-mkl@pengutronix.de


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