ARM: dts: vf610-zii-cfu1: Add SFF interface to switch

The switch has an SFF attached to port 5. Add the SFF device, the
pinmux for its GPIOs, and list the port in the switch configuration.

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