PCI: mvebu: Return 'unsupported' for Interrupt Line and Interrupt Pin

The emulated bridge does not support interrupts, so it should return the
value 0 for Interrupt Line and Interrupt Pin.  This indicates that
interrupts are not supported.

Since Max_Lat and Min_Gnt are also in the same 32-bit word, we return
0 for them, which means "do not care."

This corrects an error message from the kernel:

  pci 0000:00:01.0: of_irq_parse_pci() failed with rc=135

Which is due to the default return of 0xFFFFFFFF indicating that
interrupts are supported.

The error message regression was caused by 16b84e5a50 ("of/irq: Create
of_irq_parse_and_map_pci() to consolidate arch code.")

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>

drivers/pci/host/pci-mvebu.c

@@ -447,6 +447,11 @@ static int mvebu_sw_pci_bridge_read(struct mvebu_pcie_port *port,
 		*value = 0;
 		break;
 
+	case PCI_INTERRUPT_LINE:
+		/* LINE PIN MIN_GNT MAX_LAT */
+		*value = 0;
+		break;
+
 	default:
 		*value = 0xffffffff;
 		return PCIBIOS_BAD_REGISTER_NUMBER;