drivers/vpd: Add support to read device serial from VPD

Add functions to read the system and mainboard serial numbers
from VPD tables stored in flash.

Remove board-specific implementations for google/drallion and
google/sarien and select the new Kconfig instead.

Test: build/boot google/akemi with RO_VPD region persisted from
stock Google firmware, verify system/mainboard serial numbers
present via dmidecode.

Change-Id: I14ae07cd8b764e1e22d58577c7cc697ca1496bd5
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49050
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/vpd/Kconfig

@@ -19,3 +19,8 @@ config VPD_FMAP_SIZE
 	default 0x4000
 	help
 	  Size in bytes of the FMAP region created to store VPD tables.
+
+config SMBIOS_SERIAL_FROM_VPD
+	bool "Load device serial from VPD"
+	depends on VPD && GENERATE_SMBIOS_TABLES
+	default n

src/drivers/vpd/Makefile.inc

@@ -5,3 +5,4 @@ verstage-$(CONFIG_VPD) += vpd_decode.c vpd.c
 romstage-$(CONFIG_VPD) += vpd_decode.c vpd.c
 postcar-$(CONFIG_VPD) += vpd_decode.c vpd.c
 ramstage-$(CONFIG_VPD) += vpd_decode.c vpd.c
+ramstage-$(CONFIG_SMBIOS_SERIAL_FROM_VPD) += vpd_serial.c

src/drivers/vpd/vpd_serial.c

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#include <smbios.h>
+
+#include "vpd.h"
+#include "vpd_tables.h"
+
+#define VPD_KEY_SYSTEM_SERIAL		"serial_number"
+#define VPD_KEY_MAINBOARD_SERIAL	"mlb_serial_number"
+#define VPD_SERIAL_LEN			64
+
+const char *smbios_system_serial_number(void)
+{
+	static char serial[VPD_SERIAL_LEN];
+	if (vpd_gets(VPD_KEY_SYSTEM_SERIAL, serial, VPD_SERIAL_LEN, VPD_RO))
+		return serial;
+	return "";
+}
+
+const char *smbios_mainboard_serial_number(void)
+{
+	static char serial[VPD_SERIAL_LEN];
+	if (vpd_gets(VPD_KEY_MAINBOARD_SERIAL, serial, VPD_SERIAL_LEN, VPD_RO))
+		return serial;
+	return "";
+}