mb/google/poppy/variants/nautilus: Add SKU info to SMBIOS

This change provides implementation of smbios_mainboard_sku() to add
proper "skuX" string to SMBIOS table 1.

BUG=b:112163362
TEST=Verified "dmidecode -t 1" reports skuX correctly.

Change-Id: I7e42d2c80d791ea7170d066d2eeaa0c6811eb9c9
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/27862
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

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

@@ -17,6 +17,8 @@
 #include <chip.h>
 #include <gpio.h>
 #include <device/device.h>
+#include <smbios.h>
+#include <string.h>
 #include <variant/sku.h>
 
 uint32_t variant_board_sku(void)
@@ -40,6 +42,15 @@ uint32_t variant_board_sku(void)
 	return sku_id;
 }
 
+const char *smbios_mainboard_sku(void)
+{
+	static char sku_str[5]; /* sku{0-1} */
+
+	snprintf(sku_str, sizeof(sku_str), "sku%u", variant_board_sku());
+
+	return sku_str;
+}
+
 /* Override dev tree settings per board */
 void variant_devtree_update(void)
 {