PCI: imx6: Add helper function imx_pcie_add_lut_by_rid()

Add helper function imx_pcie_add_lut_by_rid(), which will be used by the
upcoming LUT configuration for MSI/IOMMU in the Endpoint mode. No
functional change.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
[mani: reworded commit message and dropped tested-by tag]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250710-ep-msi-v21-1-57683fc7fb25@nxp.com

Author: nxpfrankli

drivers/pci/controller/dwc/pci-imx6.c

@@ -1096,18 +1096,14 @@ static void imx_pcie_remove_lut(struct imx_pcie *imx_pcie, u16 rid)
 	}
 }
 
-static int imx_pcie_enable_device(struct pci_host_bridge *bridge,
-				  struct pci_dev *pdev)
+static int imx_pcie_add_lut_by_rid(struct imx_pcie *imx_pcie, u32 rid)
 {
-	struct imx_pcie *imx_pcie = to_imx_pcie(to_dw_pcie_from_pp(bridge->sysdata));
-	u32 sid_i, sid_m, rid = pci_dev_id(pdev);
+	struct device *dev = imx_pcie->pci->dev;
 	struct device_node *target;
-	struct device *dev;
+	u32 sid_i, sid_m;
 	int err_i, err_m;
 	u32 sid = 0;
 
-	dev = imx_pcie->pci->dev;
-
 	target = NULL;
 	err_i = of_map_id(dev->of_node, rid, "iommu-map", "iommu-map-mask",
 			  &target, &sid_i);
@@ -1182,6 +1178,13 @@ static int imx_pcie_enable_device(struct pci_host_bridge *bridge,
 	return imx_pcie_add_lut(imx_pcie, rid, sid);
 }
 
+static int imx_pcie_enable_device(struct pci_host_bridge *bridge, struct pci_dev *pdev)
+{
+	struct imx_pcie *imx_pcie = to_imx_pcie(to_dw_pcie_from_pp(bridge->sysdata));
+
+	return imx_pcie_add_lut_by_rid(imx_pcie, pci_dev_id(pdev));
+}
+
 static void imx_pcie_disable_device(struct pci_host_bridge *bridge,
 				    struct pci_dev *pdev)
 {