rust: alloc: kbox: Add AsRef implementation to Box

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>

Author: WhatAmISupposedToPutHere

rust/kernel/alloc/kbox.rs

@@ -536,3 +536,13 @@ where
         unsafe { A::free(self.0.cast(), layout) };
     }
 }
+
+impl<T, A> AsRef<T> for Box<T, A>
+where
+    T: ?Sized,
+    A: Allocator,
+{
+    fn as_ref(&self) -> &T {
+        &**self
+    }
+}