Fix typo in the first error message printed by rcar_can_open().

Based on the original patch by Vladimir Barinov.

Fixes: 862e2b6a ("can: rcar_can: support all input clocks")
Reported-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>