mb/google/dedede/var/galith: Add Wifi SAR for convertibles

Add wifi sar for galith
Using convertible mode of fw config to decide to load custom wifi sar or not.

BUG=b:176206495
TEST=enable CHROMEOS_WIFI_SAR in config of coreboot,
emerge-dedede coreboot-private-files-baseboard-dedede coreboot chromeos-bootimage.

Cq-Depend: chromium:2649378,chrome-internal:3559387
Signed-off-by: FrankChu <frank_chu@pegatron.corp-partner.google.com>
Change-Id: I0f9a7ddedef550317da4bf798317619ffd1fa979
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49923
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/dedede/Kconfig.name

@@ -85,6 +85,7 @@ config BOARD_GOOGLE_GALTIC
 	bool "-> Galtic"
 	select BOARD_GOOGLE_BASEBOARD_DEDEDE
 	select BASEBOARD_DEDEDE_LAPTOP
+	select GEO_SAR_ENABLE if CHROMEOS_WIFI_SAR
 
 config BOARD_GOOGLE_SASUKE
 	bool "-> Sasuke"

src/mainboard/google/dedede/variants/galtic/Makefile.inc

@@ -1,3 +1,5 @@
 ## SPDX-License-Identifier: GPL-2.0-or-later
 
+ramstage-$(CONFIG_FW_CONFIG) += variant.c
+
 ramstage-y += gpio.c

src/mainboard/google/dedede/variants/galtic/variant.c

@@ -0,0 +1,13 @@
+/* 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(TABLETMODE, TABLETMODE_ENABLED)))
+		filename = "wifi_sar-galtic.hex";
+	return filename;
+}