ksud: fix issues found by clippy (#167)

These issues are mostly found by `cargo clippy -- -W clippy::pedantic`.

userspace/ksud/src/debug.rs

@@ -55,7 +55,7 @@ pub fn set_manager(pkg: &str) -> Result<()> {
     );
 
     let path = get_apk_path(pkg).with_context(|| format!("{pkg} does not exist!"))?;
-    let sign = get_apk_signature(path.as_str())?;
+    let sign = get_apk_signature(&path)?;
     set_kernel_param(sign.0, sign.1)?;
     Ok(())
 }