ARM: dts: imx6: RDU2: Add Switch EEPROM

The Marvell switch has an EEPROM connected to it. List the size in DT,
in order to enable access to it via ethtool.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Chris Healy <cphealy@gmail.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>