mb/lenovo: Add SMBIOS type 9 for ExpressCard

Mark all known PCIe root ports as ExpressCard slot.

Tested on Lenovo T520.

Change-Id: I43fb481512a54ee054c6fd0189053028fb3c3ec2
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32309
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/lenovo/t420/devicetree.cb b/src/mainboard/lenovo/t420/devicetree.cb
index 47c14ef..c4092fe 100644
--- a/src/mainboard/lenovo/t420/devicetree.cb
+++ b/src/mainboard/lenovo/t420/devicetree.cb
@@ -94,6 +94,7 @@
 			device pci 1c.2 off end # PCIe Port #3
 			device pci 1c.3 on
 				subsystemid 0x17aa 0x21ce
+				smbios_slot_desc "7" "3" "ExpressCard Slot" "8"
 			end # PCIe Port #4 ExpressCard
 			device pci 1c.4 on
 				subsystemid 0x17aa 0x21ce