PCI: generic: Fix lookup of linux,pci-probe-only property

When pci-host-generic looks for the probe-only property, it seems to trust
the DT to be correctly written, and assumes that there is a parameter to
the property.

Unfortunately, this is not always the case, and some firmware expose this
property naked.  The driver ends up making a decision based on whatever the
property pointer points to, which is likely to be junk.

Switch to the common of_pci.c implementation that doesn't suffer from this
problem.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>

drivers/pci/host/pci-host-generic.c

@@ -210,7 +210,6 @@ static int gen_pci_probe(struct platform_device *pdev)
 	int err;
 	const char *type;
 	const struct of_device_id *of_id;
-	const int *prop;
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
@@ -225,13 +224,7 @@ static int gen_pci_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	prop = of_get_property(of_chosen, "linux,pci-probe-only", NULL);
-	if (prop) {
-		if (*prop)
-			pci_add_flags(PCI_PROBE_ONLY);
-		else
-			pci_clear_flags(PCI_PROBE_ONLY);
-	}
+	of_pci_check_probe_only();
 
 	of_id = of_match_node(gen_pci_of_match, np);
 	pci->cfg.ops = of_id->data;