rust: cpufreq: fix formatting

We do our best to keep the repository `rustfmt`-clean, thus run the tool
to fix the formatting issue.

Link: https://docs.kernel.org/rust/coding-guidelines.html#style-formatting
Link: https://rust-for-linux.com/contributing#submit-checklist-addendum


Fixes: f97aef09 ("cpufreq: Make drivers using CPUFREQ_ETERNAL specify transition latency")
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>