mb/google/rex: Implement WIFI SAR related changes

1. Add CHROMEOS_WIFI_SAR to include the SAR configs.
2. Add get_wifi_sar_cbfs_file_name() that return the wifi SAR
   filename.

BUG=none
TEST=emerge-rex coreboot

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: Ia863eaa53c9456ae0e9f0e8914e0de497a32b53b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68393
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ivy Jian <ivy.jian@quanta.corp-partner.google.com>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

src/mainboard/google/rex/Kconfig

@@ -46,6 +46,14 @@ config CHROMEOS
 	select GBB_FLAG_FORCE_MANUAL_RECOVERY
 	select HAS_RECOVERY_MRC_CACHE
 
+config CHROMEOS_WIFI_SAR
+	bool "Enable SAR options for ChromeOS build"
+	depends on CHROMEOS
+	select DSAR_ENABLE
+	select GEO_SAR_ENABLE
+	select SAR_ENABLE
+	select USE_SAR
+
 config DEVICETREE
 	default "variants/baseboard/\$(CONFIG_BASEBOARD_DIR)/devicetree.cb"
 

src/mainboard/google/rex/variants/rex0/Makefile.inc

@@ -1,3 +1,4 @@
 bootblock-y += gpio.c
 romstage-y += gpio.c
 ramstage-y += gpio.c
+ramstage-y += variant.c

src/mainboard/google/rex/variants/rex0/variant.c

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <sar.h>
+
+const char *get_wifi_sar_cbfs_filename(void)
+{
+	return "wifi_sar_0.hex";
+}