scripts: generate_rust_analyzer: Add ffi crate

scripts: generate_rust_analyzer: Add ffi crate

Commit d072acda4862 ("rust: use custom FFI integer types") did not
update rust-analyzer to include the new crate.

To enable rust-analyzer support for these custom ffi types, add the
`ffi` crate as a dependency to the `bindings`, `uapi` and `kernel`
crates, which all directly depend on it.

Fixes: d072acda4862 ("rust: use custom FFI integer types")
Signed-off-by: Lukas Fischer <kernel@o1oo11oo.de>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250404125150.85783-2-kernel@o1oo11oo.de
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>