mb/google/brya/var/redrix: Get wifi sar name

Add get_wifi_sar_cbfs_file_name() to return the wifi SAR file name

BUG=None
TEST=FW_NAME=redrix emerge-brya coreboot

Change-Id: I87e7a30619fd93d0eae692c4c540c29850ff6721
Signed-off-by: Wisley Chen <wisley.chen@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57710
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/google/brya/variants/redrix/Makefile.inc

@@ -4,3 +4,5 @@ bootblock-y += gpio.c
 ramstage-y += gpio.c
 
 ramstage-$(CONFIG_FW_CONFIG) += fw_config.c
+
+ramstage-y += variant.c

src/mainboard/google/brya/variants/redrix/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";
+}