mb/lenovo/x131e: remove reference to non-existent file

In commit 7f5efd90e (intel/bd82x6x: Use generated ACPI PIRQ)
the default_irq_route.asl file was removed, but this mainboard
was missed. Follow suit with the original intent of the commit
and fix the build breakage.

Change-Id: Iac233b802239e4e5cfc66d9545bb637ec4f9f541
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/22958
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/mainboard/lenovo/x131e/dsdt.asl

@@ -42,7 +42,6 @@ DefinitionBlock(
 			#include <northbridge/intel/sandybridge/acpi/sandybridge.asl>
 			#include <drivers/intel/gma/acpi/default_brightness_levels.asl>
 			#include <southbridge/intel/bd82x6x/acpi/pch.asl>
-			#include <southbridge/intel/bd82x6x/acpi/default_irq_route.asl>
 		}
 	}
 }