cros_ec: Add support for reading the SKU ID

This allows reading strapping pins attached to the EC. Add an
implementation for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/misc/cros_ec_sandbox.c b/drivers/misc/cros_ec_sandbox.c
index 1922a9c..9324384 100644
--- a/drivers/misc/cros_ec_sandbox.c
+++ b/drivers/misc/cros_ec_sandbox.c
@@ -473,6 +473,13 @@
 		len = sizeof(*resp);
 		break;
 	}
+	case EC_CMD_GET_SKU_ID: {
+		struct ec_sku_id_info *resp = resp_data;
+
+		resp->sku_id = 1234;
+		len = sizeof(*resp);
+		break;
+	}
 	default:
 		printf("   ** Unknown EC command %#02x\n", req_hdr->command);
 		return -1;