can: dev: add missing of_node_put() after calling of_get_child_by_name()

of_node_put() needs to be called when the device node which is got
from of_get_child_by_name() finished using.

Fixes: 2290aefa ("can: dev: Add support for limiting configured bitrate")
Cc: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>