Correct clippy warnings

Currently intended to be done with:
cargo clippy --features "recommended merlin batch serialize experimental 
ed25519 ristretto p256 secp256k1 multisig" -- -A clippy::type_complexity 
-A dead_code

coins/ethereum/src/crypto.rs

@@ -41,7 +41,8 @@ pub fn ecrecover(message: Scalar, v: u8, r: Scalar, s: Scalar) -> Option<[u8; 20
       return Some(address(&key));
     }
   }
-  return None;
+
+  None
 }
 
 #[derive(Clone, Default)]