mb/google/dedede/var/drawcia: Add Wifi SAR for drawcia

drawman/drawlat/drawcia share the same coreboot, and only drawcia is convertible.
Use tablet mode of fw config to decide to load custom wifi sar or not.

BUG=b:165613510
TEST=enable CHROMEOS_WIFI_SAR in config of coreboot,
emerge-dedede coreboot-private-files-baseboard-dedede coreboot chromeos-bootimage.

Change-Id: Ibcd498021e63d0a172c71c3d94b60b3a25973467
Signed-off-by: Wisley Chen <wisley.chen@quantatw.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44661
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/dedede/Kconfig.name

@@ -20,6 +20,7 @@ config BOARD_GOOGLE_DRAWCIA
 	select BOARD_GOOGLE_BASEBOARD_DEDEDE
 	select BASEBOARD_DEDEDE_LAPTOP
 	select DRIVERS_GENERIC_MAX98357A
+	select GEO_SAR_ENABLE if CHROMEOS_WIFI_SAR
 
 config BOARD_GOOGLE_DRAWCIA_LEGACY
 	bool "Drawcia (Legacy)"

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

@@ -0,0 +1,3 @@
+## SPDX-License-Identifier: GPL-2.0-or-later
+
+ramstage-$(CONFIG_FW_CONFIG) += variant.c

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

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <bootstate.h>
+#include <console/console.h>
+#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-drawcia.hex";
+
+	printk(BIOS_INFO, "SAR file name: %s\n", filename);
+	return filename;
+}