net: phy: Make phy_10gbit_fec_features_array static

This array is not used outside of phy_device.c, so make it static.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>