ACPI: Make sure we call acpi_register_gsi() even for default PCI interrupt assignment

That's the part that keeps track of the ELCR register, and we want to
make sure that the PCI interrupts are properly marked level/low.

drivers/acpi/pci_irq.c

@@ -435,6 +435,7 @@ acpi_pci_irq_enable (
 		/* Interrupt Line values above 0xF are forbidden */
 		if (dev->irq >= 0 && (dev->irq <= 0xF)) {
 			printk(" - using IRQ %d\n", dev->irq);
+			acpi_register_gsi(dev->irq, ACPI_LEVEL_SENSITIVE, ACPI_ACTIVE_LOW);
 			return_VALUE(0);
 		}
 		else {