sim: Remove pointless use lines

Top-level crates are available by name.  A use of these names is
redundant, so remove these.

Signed-off-by: David Brown <david.brown@linaro.org>

sim/mcuboot-sys/src/api.rs

@@ -6,7 +6,6 @@
 //! HAL api for MyNewt applications
 
 use crate::area::CAreaDesc;
-use libc;
 use log::{Level, log_enabled, warn};
 use simflash::{Result, Flash, FlashPtr};
 use std::{

sim/mcuboot-sys/src/c.rs

@@ -82,7 +82,6 @@ pub fn kw_encrypt(kek: &[u8], seckey: &[u8]) -> Result<[u8; 24], &'static str> {
 mod raw {
     use crate::area::CAreaDesc;
     use crate::api::CSimContext;
-    use libc;
 
     extern "C" {
         // This generates a warning about `CAreaDesc` not being foreign safe.  There doesn't appear to

sim/src/main.rs

@@ -3,10 +3,6 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
-use env_logger;
-
-use bootsim;
-
 fn main() {
     env_logger::init();
 

sim/src/testlog.rs

@@ -11,7 +11,6 @@
 //! function, which should be called at the beginning of each test, will setup logging for all of
 //! the tests.
 
-use env_logger;
 use std::sync::Once;
 
 static INIT: Once = Once::new();

sim/src/tlv.rs

@@ -17,8 +17,6 @@ use byteorder::{
     LittleEndian, WriteBytesExt,
 };
 use crate::image::ImageVersion;
-use pem;
-use base64;
 use log::info;
 use ring::{digest, rand, agreement, hkdf, hmac};
 use ring::rand::SecureRandom;