clippy: Fix more pedantic warnings

src/cec.rs

@@ -55,6 +55,7 @@ impl fmt::Display for HdmiCecState {
 }
 
 impl HdmiCecState {
+    #[must_use]
     pub fn to_human_readable(&self) -> &'static str {
         match self {
             HdmiCecState::Disabled => "disabled",

src/proxy/mod.rs

@@ -5,6 +5,8 @@
  * SPDX-License-Identifier: MIT
  */
 
+#![allow(clippy::module_name_repetitions)]
+
 // Re-export relevant proxies
 
 // TODO Some of these should get renamed