misc: Address clippy beta issues

Signed-off-by: Bo Chen <chen.bo@intel.com>

vm-device/src/bus.rs

@@ -110,8 +110,7 @@ impl Bus {
         let devices = self.devices.read().unwrap();
         let (range, dev) = devices
             .range(..=BusRange { base: addr, len: 1 })
-            .rev()
-            .next()?;
+            .next_back()?;
         dev.upgrade().map(|d| (*range, d.clone()))
     }