arch: Move crate to rust 2018 edition

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

arch/src/x86_64/smbios.rs

@@ -6,7 +6,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 
-use layout::SMBIOS_START;
+use crate::layout::SMBIOS_START;
 use std::fmt::{self, Display};
 use std::mem;
 use std::result;