mb/google/poppy/variants/nami: Define smbios_mainboard_sku to return SKU IDs

Return proper SKU IDs so that mosys can return the proper variant.

BUG=b:74059798
BRANCH=None
TEST=./util/abuild/abuild -p none -t google/poppy -x -a

Change-Id: I665fa491de6e277fea5cc071b1f04a21317bccba
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://review.coreboot.org/25028
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/mainboard/google/poppy/variants/nami/mainboard.c

@@ -13,10 +13,15 @@
  * GNU General Public License for more details.
  */
 
+#include <arch/cpu.h>
+#include <assert.h>
+#include <baseboard/variants.h>
 #include <chip.h>
 #include <device/device.h>
 #include <ec/google/chromeec/ec.h>
-#include <baseboard/variants.h>
+#include <smbios.h>
+#include <soc/ramstage.h>
+#include <string.h>
 
 #define SKU_UNKNOWN	0xFFFF
 #define SKU_0_NAMI	0x3A7B
@@ -49,3 +54,12 @@ void variant_devtree_update(void)
 		break;
 	}
 }
+
+const char *smbios_mainboard_sku(void)
+{
+	static char sku_str[9]; /* sku{0..65535} (basically up to FFFF) */
+
+	snprintf(sku_str, sizeof(sku_str), "sku%d", board_sku_id());
+
+	return sku_str;
+}