rust: arc: move Receiver for ArcBorrow<'_, T>

This is part of the effort to minimize the differences of the `rust`
branch with respect to mainline in order to eventually drop it.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

rust/kernel/sync/arc.rs

@@ -130,9 +130,6 @@ struct ArcInner<T: ?Sized> {
 // This is to allow [`Arc`] (and variants) to be used as the type of `self`.
 impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
 
-// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
-impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
-
 // This is to allow coercion from `Arc<T>` to `Arc<U>` if `T` can be converted to the
 // dynamically-sized type (DST) `U`.
 impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
@@ -436,6 +433,9 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
     _p: PhantomData<&'a ()>,
 }
 
+// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
+impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
+
 impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
     fn clone(&self) -> Self {
         *self