ARM: orion5x: Fix typo in device_type property of phy node

This patch fixes a typo for device_type property of phy node.
This can work as of today but once a checks are added in generic code
this typo will stop phy from working.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>