sconfig: Add SMBIOS type 9 entries

Add the new field 'smbios_slot_desc', which takes 2 to 4 arguments.
The field is valid for PCI devices and only compiled if SMBIOS table
generation is enabled.

smbios_slot_desc arguments:
1. slot type
2. slot lenth
3. slot designation (optional)
4. slot data width (optional)

Example:

    device pci 1c.1 on
        smbios_slot_desc "21" "3" "MINI-PCI-FULL" "8"
    end # PCIe Port #2 Integrated Wireless LAN

Tested on Lenovo T520.

Change-Id: If95aae3c322d3da47637613b9a872ba1f7af9080
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32307
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

src/include/device/device.h

@@ -141,6 +141,12 @@ struct device {
 #if !DEVTREE_EARLY
 	struct chip_operations *chip_ops;
 	const char *name;
+#if CONFIG(GENERATE_SMBIOS_TABLES)
+	u8 smbios_slot_type;
+	u8 smbios_slot_data_width;
+	u8 smbios_slot_length;
+	const char *smbios_slot_designation;
+#endif
 #endif
 	DEVTREE_CONST void *chip_info;
 };