ARM: dts: vf610-zii: Add switch eeprom-length properties

Two of the Ethernet switches on this board have EEPROMs connected.
Add the eeprom-length property to the device tree, making it possible
to access the EEPROM using ethtool -e.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>