rust: init: Implement Zeroable::zeroed()

By analogy to Default::default(), this just returns the zeroed
representation of the type directly. init::zeroed() is the version that
returns an initializer.

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

rust/kernel/init.rs

@@ -1350,7 +1350,14 @@ pub unsafe trait PinnedDrop: __internal::HasPinData {
 /// ```rust,ignore
 /// let val: Self = unsafe { core::mem::zeroed() };
 /// ```
-pub unsafe trait Zeroable {}
+pub unsafe trait Zeroable: core::marker::Sized {
+    /// Create a new zeroed T.
+    ///
+    /// Directly returns a zeroed T, analogous to Default::default().
+    fn zeroed() -> Self {
+        unsafe { core::mem::zeroed() }
+    }
+}
 
 /// Create a new zeroed T.
 ///