ARM: dts: vf610-zii-dev-rev-c: add support for one SFF module

The board typically has 2 populated SFF interfaces. The mv88e6xxx
driver currently supports SFF modules connected to ports 9 and 10 of
the mv88e6390. Add support for sff2, which is connected to port 9.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>