coding-style: Clarify the expectations around bool

There has been some confusion since checkpatch started warning about bool
use in structures, and people have been avoiding using it.

Many people feel there is still a legitimate place for bool in structures,
so provide some guidance on bool usage derived from the entire thread that
spawned the checkpatch warning.

Link: https://lkml.kernel.org/r/CA+55aFwVZk1OfB9T2v014PTAKFhtVan_Zj2dOjnCy3x6E4UJfA@mail.gmail.com


Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Joe Perches <joe@perches.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>