PCI: dwc: Convert dw_pcie_link_up() to use dw_pcie_readl_dbi()

While the rest of the generic DWC PCIe code uses the dedicated IO-mem
accessors, the dw_pcie_link_up() method for some unobvious reason directly
calls readl() to get PortLogic.DEBUG1 register content. Since the way the
DBI bus is accessed can be platform-specific, use dw_pcie_readl_dbi()
instead so dw_pcie_link_up() is slightly more generic.

Link: https://lore.kernel.org/r/20220624143428.8334-11-Sergey.Semin@baikalelectronics.ruTested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>

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

@@ -548,7 +548,7 @@ int dw_pcie_link_up(struct dw_pcie *pci)
 	if (pci->ops && pci->ops->link_up)
 		return pci->ops->link_up(pci);
 
-	val = readl(pci->dbi_base + PCIE_PORT_DEBUG1);
+	val = dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1);
 	return ((val & PCIE_PORT_DEBUG1_LINK_UP) &&
 		(!(val & PCIE_PORT_DEBUG1_LINK_IN_TRAINING)));
 }