cosmetic: replace boolean function return values with bool

cosmetic: replace boolean function return values with bool

For functions that test if something is true/valid and return a 1
or 0, it makes sense to switch to bool.

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>