Note that in mainline, `ffi` (the crate) still redirects to
`core::ffi`, since we split the change in 2 kernel cycles to make it
easier to migrate. But in `rust-next`, `ffi` (the crate) already uses
the new mapping.
The idea is that you can already use `ffi` (the crate) -- so please use that.
I hope that helps!
Cheers,
Miguel