The .id member of the struct device for the invm device is not
initialized and so implicitly zero. This yields:

	register_device: already registered invm0

for the second i210 during probe.

So use the parent's id to initialize the id for invm, too, as is already
done for the corresponding e1000-nor device.

Fixes: a74b97f009c6 ("e1000: Expose i210's iNVM as a cdev")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>