build: Remove unnecessary Result<> returns

If the function can never return an error this is now a clippy failure:

error: this function's return value is unnecessarily wrapped by `Result`
   --> virtio-devices/src/watchdog.rs:215:5
    |
215 | /     fn set_state(&mut self, state: &WatchdogState) -> io::Result<()> {
216 | |         self.common.avail_features = state.avail_features;
217 | |         self.common.acked_features = state.acked_features;
218 | |         // When restoring enable the watchdog if it was previously enabled. We reset the timer
...   |
223 | |         Ok(())
224 | |     }
    | |_____^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_wraps

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

vmm/src/cpu.rs

@@ -992,12 +992,11 @@ impl CpuManager {
         Ok(())
     }
 
-    fn mark_vcpus_for_removal(&mut self, desired_vcpus: u8) -> Result<()> {
+    fn mark_vcpus_for_removal(&mut self, desired_vcpus: u8) {
         // Mark vCPUs for removal, actual removal happens on ejection
         for cpu_id in desired_vcpus..self.present_vcpus() {
             self.vcpu_states[usize::from(cpu_id)].removing = true;
         }
-        Ok(())
     }
 
     fn remove_vcpu(&mut self, cpu_id: u8) -> Result<()> {
@@ -1049,7 +1048,10 @@ impl CpuManager {
                 self.activate_vcpus(desired_vcpus, true)?;
                 Ok(true)
             }
-            cmp::Ordering::Less => self.mark_vcpus_for_removal(desired_vcpus).and(Ok(true)),
+            cmp::Ordering::Less => {
+                self.mark_vcpus_for_removal(desired_vcpus);
+                Ok(true)
+            }
             _ => Ok(false),
         }
     }