rust: sync: allow type of self to be Arc<T> or variants

This allows associated functions whose `self` argument has `Arc<T>` or
variants as their type. This, in turn, allows callers to use the dot
syntax to make calls.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/kernel/lib.rs

@@ -14,6 +14,7 @@
 #![no_std]
 #![feature(allocator_api)]
 #![feature(core_ffi_c)]
+#![feature(receiver_trait)]
 
 // Ensure conditional compilation based on the kernel configuration works;
 // otherwise we may silently break things like initcall handling.