PCI: tegra194: Rename 'root_bus' to 'root_port_bus' in tegra_pcie_downstream_dev_to_D0()

In tegra_pcie_downstream_dev_to_D0(), PCI devices are transitioned to D0
state. For iterating over the devices, first the downstream bus of the Root
Port is searched from the root bus. But the name of the variable that holds
the Root Port downstream bus is named as 'root_bus', which is wrong.

Rename the variable to 'root_port_bus'. Also, move the comment on 'bringing
the devices to D0' to where the state is set exactly.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250922081057.15209-1-mani@kernel.org

Author: Manivannan Sadhasivam

drivers/pci/controller/dwc/pcie-tegra194.c

@@ -1270,7 +1270,7 @@ static int tegra_pcie_bpmp_set_pll_state(struct tegra_pcie_dw *pcie,
 static void tegra_pcie_downstream_dev_to_D0(struct tegra_pcie_dw *pcie)
 {
 	struct dw_pcie_rp *pp = &pcie->pci.pp;
-	struct pci_bus *child, *root_bus = NULL;
+	struct pci_bus *child, *root_port_bus = NULL;
 	struct pci_dev *pdev;
 
 	/*
@@ -1283,19 +1283,19 @@ static void tegra_pcie_downstream_dev_to_D0(struct tegra_pcie_dw *pcie)
 	 */
 
 	list_for_each_entry(child, &pp->bridge->bus->children, node) {
-		/* Bring downstream devices to D0 if they are not already in */
 		if (child->parent == pp->bridge->bus) {
-			root_bus = child;
+			root_port_bus = child;
 			break;
 		}
 	}
 
-	if (!root_bus) {
-		dev_err(pcie->dev, "Failed to find downstream devices\n");
+	if (!root_port_bus) {
+		dev_err(pcie->dev, "Failed to find downstream bus of Root Port\n");
 		return;
 	}
 
-	list_for_each_entry(pdev, &root_bus->devices, bus_list) {
+	/* Bring downstream devices to D0 if they are not already in */
+	list_for_each_entry(pdev, &root_port_bus->devices, bus_list) {
 		if (PCI_SLOT(pdev->devfn) == 0) {
 			if (pci_set_power_state(pdev, PCI_D0))
 				dev_err(pcie->dev,