misc: Remove unnecessary "extern crate"

Now all crates use edition = "2018" then the majority of the "extern
crate" statements can be removed. Only those for importing macros need
to remain.

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

vmm/src/memory_manager.rs

@@ -2,7 +2,6 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 //
-extern crate hypervisor;
 #[cfg(target_arch = "x86_64")]
 use crate::config::SgxEpcConfig;
 use crate::config::{HotplugMethod, MemoryConfig, MemoryZoneConfig};