PCI: keystone: Defer probing if devm_phy_get() returns -EPROBE_DEFER

A SerDes PHY is optional, so if devm_phy_get() doesn't find one at all,
that's fine.  But if devm_phy_get() finds a PHY that doesn't have a driver
yet, it returns -EPROBE_DEFER.  In that case, defer probing the Keystone
driver.  We may be able to load it later after a PHY driver is loaded.

[bhelgaas: changelog, check for -EPROBE_DEFER first]
Signed-off-by: NShawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/pci/host/pci-keystone.c

@@ -359,6 +359,9 @@ static int __init ks_pcie_probe(struct platform_device *pdev)
 
 	/* initialize SerDes Phy if present */
 	phy = devm_phy_get(dev, "pcie-phy");
+	if (PTR_ERR_OR_ZERO(phy) == -EPROBE_DEFER)
+		return PTR_ERR(phy);
+
 	if (!IS_ERR_OR_NULL(phy)) {
 		ret = phy_init(phy);
 		if (ret < 0)