rust: types: add `Either` type

Introduce the new `types` module of the `kernel` crate with
`Either` as its first type.

`Either<L, R>` is a sum type that always holds either a value
of type `L` (`Left` variant) or `R` (`Right` variant).

For instance:

    struct Executor {
        queue: Either<BoxedQueue, &'static Queue>,
    }

Signed-off-by: Wedson Almeida Filho <[email protected]>
Reviewed-by: Wei Liu <[email protected]>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <[email protected]>

0 files changed, 0 insertions, 0 deletions