kmc-solid: Address compiler warnings

Addresses the warn-by-default lints `unused_imports` and
`unused_unsafe`.

library/std/src/sys/itron/condvar.rs

@@ -71,7 +71,7 @@ impl Condvar {
             }
         }
 
-        unsafe { mutex.lock() };
+        mutex.lock();
     }
 
     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
@@ -109,7 +109,7 @@ impl Condvar {
         // we woke up because of `notify_*`.
         let success = self.waiters.with_locked(|waiters| unsafe { !waiters.remove(waiter) });
 
-        unsafe { mutex.lock() };
+        mutex.lock();
         success
     }
 }

library/std/src/sys/itron/mutex.rs

@@ -72,7 +72,7 @@ pub(super) struct MutexGuard<'a>(&'a Mutex);
 impl<'a> MutexGuard<'a> {
     #[inline]
     pub(super) fn lock(x: &'a Mutex) -> Self {
-        unsafe { x.lock() };
+        x.lock();
         Self(x)
     }
 }

library/std/src/sys/solid/os.rs

@@ -1,7 +1,6 @@
 use super::unsupported;
-use crate::convert::TryFrom;
 use crate::error::Error as StdError;
-use crate::ffi::{CStr, CString, OsStr, OsString};
+use crate::ffi::{CStr, OsStr, OsString};
 use crate::fmt;
 use crate::io;
 use crate::os::{