bindings: rust: drop unneeded Arc within Chip

bindings: rust: drop unneeded Arc within Chip

Chip was modeled with an Arc that only was used to pass the chip pointer
to the chip::Info constructor. With that refactored to take a reference,
we can just drop the Arc.

This allows to get rid of the `Internal` helper struct that was only
required by the Arc.

As a side-effect, we also get rid of this clippy warning:

  warning: usage of an `Arc` that is not `Send` or `Sync`
    --> libgpiod/src/chip.rs:75:21
     |
  75 |         let ichip = Arc::new(Internal::open(path)?);
     |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |
     = note: the trait `Send` is not implemented for `Internal`
     = note: the trait `Sync` is not implemented for `Internal`
     = note: required for `Arc<Internal>` to implement `Send` and `Sync`
     = help: consider using an `Rc` instead or wrapping the inner type with a `Mutex`

Signed-off-by: Erik Schilling <erik.schilling@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>