staging: mt7621-pci: add phy exit call if phy_power_on call fails

Add missing call to 'phy_exit' function if the phy_power_on call fails.
With this call added the error path is properly handled.

Fixes: 07420a02 ("staging: mt7621-pci: use gpio perst instead of builtin behaviour")
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-pci/pci-mt7621.c

@@ -436,6 +436,7 @@ static int mt7621_pcie_init_port(struct mt7621_pcie_port *port)
 	err = phy_power_on(port->phy);
 	if (err) {
 		dev_err(dev, "failed to power on port%d phy\n", slot);
+		phy_exit(port->phy);
 		return err;
 	}