rust/kernel: Add faux device bindings

This introduces a module for working with faux devices in rust, along with
adding sample code to show how the API is used. Unlike other types of
devices, we don't provide any hooks for device probe/removal - since these
are optional for the faux API and are unnecessary in rust.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Maíra Canal <mairacanal@riseup.net>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>