rust: kbuild: remove "dummy parameter" workaround for `bindgen` < 0.71.1
Until the version bump of `bindgen`, we needed to pass a dummy parameter
to avoid failing the `--version` call.
Thus remove it.
Reviewed-by: Tamir Duberstein <tamird@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260405235309.418950-22-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>