PCI: rcar: Fix bridge logic configuration accesses

The bridge logic at slot 0 only supports reads up to 0x40 and the rest of
the PCI configuration space for this slot is marked as reserved in the
manual.

Trying a read from offset 0x100 is producing an error from the bridge. With
error interrupts enabled, the following is printed:

  pci-rcar-gen2 ee0d0000.pci: error irq: status 00000014

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>

drivers/pci/host/pci-rcar-gen2.c

@@ -119,6 +119,10 @@ static void __iomem *rcar_pci_cfg_base(struct pci_bus *bus, unsigned int devfn,
 	if (slot > 2)
 		return NULL;
 
+	/* bridge logic only has registers to 0x40 */
+	if (slot == 0x0 && where >= 0x40)
+		return NULL;
+
 	val = slot ? RCAR_AHBPCI_WIN1_DEVICE | RCAR_AHBPCI_WIN_CTR_CFG :
 		     RCAR_AHBPCI_WIN1_HOST | RCAR_AHBPCI_WIN_CTR_CFG;