mb/google/volteer: Add WiFi SAR table support for Lindar/Lillipup

Lindar/Lillipup uses the WIFI_SAR_ID field in FW_CONFIG to pick which
SAR table to load.

BUG=b:178302811
BRANCH=volteer
TEST=build and test no lindar/lillipup

Signed-off-by: Kevin Chang <kevin.chang@lcfc.corp-partner.google.com>
Change-Id: Ibe829062033ba8246b9d9550cdcdc360f5f67dd3
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50872
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: YH Lin <yueherngl@google.com>

src/mainboard/google/volteer/variants/lindar/Makefile.inc

@@ -5,3 +5,5 @@ bootblock-y += gpio.c
 romstage-y += memory.c
 
 ramstage-y += gpio.c
+
+ramstage-$(CONFIG_FW_CONFIG) += variant.c

src/mainboard/google/volteer/variants/lindar/variant.c

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <fw_config.h>
+#include <sar.h>
+
+const char *get_wifi_sar_cbfs_filename(void)
+{
+	const char *filename = NULL;
+
+	if (fw_config_probe(FW_CONFIG(WIFI_SAR_ID, WIFI_SAR_ID_0)))
+		filename = "wifi_sar_0.hex";
+	else if (fw_config_probe(FW_CONFIG(WIFI_SAR_ID, WIFI_SAR_ID_1)))
+		filename = "wifi_sar_1.hex";
+
+	return filename;
+}