net: axienet: setup mdio unconditionally

[ Upstream commit d1c4f93e

 ]

The call to axienet_mdio_setup should not depend on whether "phy-node"
pressents on the DT. Besides, since `lp->phy_node` is used if PHY is in
SGMII or 100Base-X modes, move it into the if statement. And the next patch
will remove `lp->phy_node` from driver's private structure and do an
of_node_put on it right away after use since it is not used elsewhere.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Robert Hancock <robert.hancock@calian.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>