mb/lenovo/t440p: Disable second PEG device

PEG bifurcation is strapped to x8/x8 on this board, but only the first
port is used. Disable the PEG device at 00:01.1 because it is unused.

Should fix booting with commit ae999503f6
(nb/intel/haswell/pcie.c: Add missing pre-ASPM init). The `config_of()`
function call added in that commit makes coreboot die if any PEG device
that is enabled by strapping is not present in the devicetree. While it
is true that the PEG code should not use `config_of()`, this PEG device
should still be disabled on this board as it is never used.

Change-Id: I16809e081f9a56ba2f1fdfcb4b8289d75161056b
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55687
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Máté Kukri <kukri.mate@gmail.com>

src/mainboard/lenovo/t440p/devicetree.cb

@@ -24,6 +24,7 @@ chip northbridge/intel/haswell
 
 		device pci 00.0 on  end	# Host bridge
 		device pci 01.0 on  end	# PCIe Bridge for discrete graphics
+		device pci 01.1 off end	# Unused PCIe Bridge
 		device pci 02.0 on  end	# Internal graphics VGA controller
 		device pci 03.0 on  end	# Mini-HD audio