'clang-format' is on 'Other material' section of 'process/index', but it
may fit more under 'dev-tools/' directory.  Move it.

Signed-off-by: SeongJae Park <[email protected]>
Acked-by: Miguel Ojeda <[email protected]>
Acked-by: Federico Vaga <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]