net: phy: don't export gen10g_read_status

gen10g_read_status is deprecated, therefore stop exporting it.
We don't want to encourage anybody to use it.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>