exporting a device type

[Andy Shevchenko]

I have an issue with this change

https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/commit/?h=for-driver-core&id=e86cc69186051d7312711565803de586efd9b2cf

(I think you haven't yet sent it for review, so this is just
preliminary look at)

The idea of exporting bus type will open a non-reversible box of
changes when people will start abusing it. Instead just provide an API
dev_is_auxiliary() as it's done in other subsystems (yes, I know that
some of them are still exporting the type, but it's most likely due to
historical reasons of not thinking through it at that time).

-- 
With Best Regards,
Andy Shevchenko