Revert "PCI: dwc/keystone: Drop duplicated 'num-viewport'"

This reverts commit 421063ef.

In preparation to detect the number of iATU regions instead of using DT
properties, we need to keep reading 'num-viewport' for the Keystone
driver which doesn't use the iATU in older versions of the IP.

However, note that Keystone has been broken for some time with upstream
dts files which don't set 'num-viewports'. The reverted commit did
make the property optional, but now it's mandatory again.

Link: https://lore.kernel.org/r/20201105211159.1814485-15-robh@kernel.orgTested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/dwc/pci-keystone.c

@@ -121,6 +121,7 @@ struct keystone_pcie {
 
 	int			msi_host_irq;
 	int			num_lanes;
+	u32			num_viewport;
 	struct phy		**phy;
 	struct device_link	**link;
 	struct			device_node *msi_intc_np;
@@ -386,9 +387,9 @@ static void ks_pcie_clear_dbi_mode(struct keystone_pcie *ks_pcie)
 static void ks_pcie_setup_rc_app_regs(struct keystone_pcie *ks_pcie)
 {
 	u32 val;
+	u32 num_viewport = ks_pcie->num_viewport;
 	struct dw_pcie *pci = ks_pcie->pci;
 	struct pcie_port *pp = &pci->pp;
-	u32 num_viewport = pci->num_viewport;
 	u64 start, end;
 	struct resource *mem;
 	int i;
@@ -1093,6 +1094,7 @@ static int __init ks_pcie_probe(struct platform_device *pdev)
 	struct resource *res;
 	unsigned int version;
 	void __iomem *base;
+	u32 num_viewport;
 	struct phy **phy;
 	u32 num_lanes;
 	char name[10];
@@ -1224,6 +1226,12 @@ static int __init ks_pcie_probe(struct platform_device *pdev)
 			goto err_get_sync;
 		}
 
+		ret = of_property_read_u32(np, "num-viewport", &num_viewport);
+		if (ret < 0) {
+			dev_err(dev, "unable to read *num-viewport* property\n");
+			goto err_get_sync;
+		}
+
 		/*
 		 * "Power Sequencing and Reset Signal Timings" table in
 		 * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 2.0
@@ -1237,6 +1245,7 @@ static int __init ks_pcie_probe(struct platform_device *pdev)
 			gpiod_set_value_cansleep(gpiod, 1);
 		}
 
+		ks_pcie->num_viewport = num_viewport;
 		pci->pp.ops = host_ops;
 		ret = dw_pcie_host_init(&pci->pp);
 		if (ret < 0)