Convert literal uses of CONFIG_MAINBOARD_{VENDOR,PART_NUMBER}

Only expand these strings in lib/identity.o.

Change-Id: I8732bbeff8cf8a757bf32fdb615b1d0f97584585
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74907
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
diff --git a/src/mainboard/emulation/qemu-i440fx/northbridge.c b/src/mainboard/emulation/qemu-i440fx/northbridge.c
index 56693c3..5d24c5b 100644
--- a/src/mainboard/emulation/qemu-i440fx/northbridge.c
+++ b/src/mainboard/emulation/qemu-i440fx/northbridge.c
@@ -1,14 +1,15 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <arch/io.h>
+#include <arch/ioapic.h>
 #include <console/console.h>
 #include <cpu/cpu.h>
 #include <cpu/x86/lapic_def.h>
 #include <cpu/x86/mp.h>
-#include <arch/io.h>
 #include <device/pci_def.h>
 #include <device/pci_ops.h>
-#include <arch/ioapic.h>
 #include <device/device.h>
+#include <identity.h>
 #include <stdlib.h>
 #include <smbios.h>
 #include <types.h>
@@ -191,7 +192,7 @@
 	t->type_detail = MEMORY_TYPE_DETAIL_SYNCHRONOUS;
 	t->speed = 200;
 	t->clock_speed = 200;
-	t->manufacturer = smbios_add_string(t->eos, CONFIG_MAINBOARD_VENDOR);
+	t->manufacturer = smbios_add_string(t->eos, mainboard_vendor);
 
 	const int len = smbios_full_table_len(&t->header, t->eos);
 	*current += len;