PCI: dwc: intel: Make intel_pcie_cpu_addr() static

Fix the following sparse warning:

drivers/pci/controller/dwc/pcie-intel-gw.c:456:5: warning: symbol
'intel_pcie_cpu_addr' was not declared. Should it be static?

Link: https://lore.kernel.org/r/20200415084953.6533-1-yanaijie@huawei.comReported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/dwc/pcie-intel-gw.c

@@ -453,7 +453,7 @@ static int intel_pcie_msi_init(struct pcie_port *pp)
 	return 0;
 }
 
-u64 intel_pcie_cpu_addr(struct dw_pcie *pcie, u64 cpu_addr)
+static u64 intel_pcie_cpu_addr(struct dw_pcie *pcie, u64 cpu_addr)
 {
 	return cpu_addr + BUS_IATU_OFFSET;
 }