net: mdio: xgene: remove useless xgene_mdio_status

xgene_mdio_status is declared static, and is only written once by the
driver. It appears to have been this way since the driver was first
added to the kernel tree. No other users can be found, so let's remove
it.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>