This fixes a regression, where boards specifying the environment
path using the form device-path = &phandle, "partname:part" would
be unable to find their env.

This is due to of_find_path() switching to cdev_by_device_node()
internally, which expects the device_node member of the main
area cdev to be initialized.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>