net: phy: xgmiitorgmii: Fix non static symbol warning

Fixes the following sparse warning:

drivers/net/phy/xilinx_gmii2rgmii.c:61:5: warning:
 symbol 'xgmiitorgmii_probe' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/xilinx_gmii2rgmii.c

@@ -58,7 +58,7 @@ static int xgmiitorgmii_read_status(struct phy_device *phydev)
 	return 0;
 }
 
-int xgmiitorgmii_probe(struct mdio_device *mdiodev)
+static int xgmiitorgmii_probe(struct mdio_device *mdiodev)
 {
 	struct device *dev = &mdiodev->dev;
 	struct device_node *np = dev->of_node, *phy_node;