rust: error: Derive Error as Debug

So that `Result::expect` can be used.

Signed-off-by: Boqun Feng <[email protected]>

Author: fbq

rust/kernel/error.rs

@@ -16,6 +16,7 @@ use crate::c_types;
 ///
 /// The kernel defines a set of integer generic error codes based on C and
 /// POSIX ones. These codes may have a more specific meaning in some contexts.
+#[derive(Debug)]
 pub struct Error(c_types::c_int);
 
 impl Error {