mb/qemu/fw_cfg: Fix build when not generating SMBIOS tables

Parts of the QEMU firmware configuration device driver refers to SMBIOS
related kconfig values. These depend on GENERATE_SMBIOS_TABLES and are
undefined if it isn't enabled, causing a build error.

Cover the SMBIOS-related region in this driver with an #if directive
checking the necessary config option. This is mostly to help port the
driver to non-x86 architectures where support for generating SMBIOS
tables isn't there yet.

Change-Id: I3ff388d4574eb52686a5dda3dcbc3d64a7ce6f7b
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80366
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/emulation/qemu-i440fx/fw_cfg.c

@@ -341,6 +341,7 @@ err:
 /* ---------------------------------------------------------------------- */
 /* pick up smbios information from fw_cfg                                 */
 
+#if CONFIG(GENERATE_SMBIOS_TABLES)
 static const char *type1_manufacturer;
 static const char *type1_product_name;
 static const char *type1_version;
@@ -504,6 +505,7 @@ void smbios_system_set_uuid(u8 *uuid)
 	fw_cfg_smbios_init();
 	memcpy(uuid, type1_uuid, 16);
 }
+#endif /* CONFIG(GENERATE_SMBIOS_TABLES) */
 
 /*
  * Configure DMA setup