Some lines used spaces instead of tabs at line start.
This can cause mangled lines in editors due to inconsistency.

Replace spaces for tabs where appropriate.
Signed-off-by: NThymo van Beers <thymovanbeers@gmail.com>
Reviewed-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>