ARM: dts: imx6: RDU2: add i210 node

This is needed for the bootloader to patch in the correct MAC address.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>