[PATCH 1/3] rust: sync: implement `Default` for `LockClassKey`

[Miguel Ojeda <ojeda@kernel.org>]

In the upcoming Rust 1.78.0, Clippy suggests to implement `Default` even
when `new()` is `const`, since `Default::default()` may call `const`
functions even if it is not `const` itself [1]:

    error: you should consider adding a `Default` implementation for `LockClassKey`
      --> rust/kernel/sync.rs:31:5
       |
    31 | /     pub const fn new() -> Self {
    32 | |         Self(Opaque::uninit())
    33 | |     }
       | |_____^

Thus implement it.

Link: https://github.com/rust-lang/rust-clippy/pull/10903 [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/kernel/sync.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index c983f63fd56e..0ab20975a3b5 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -37,6 +37,12 @@ pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
     }
 }
 
+impl Default for LockClassKey {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 /// Defines a new static lock class and returns a pointer to it.
 #[doc(hidden)]
 #[macro_export]
-- 
2.44.0