clocksource/drivers/owl: fix refcount leak

[Markus Elfring]

>> How will chances evolve to adjust variable scopes accordingly?
> 
> Is this even a thing in Linux?
> I mean specifying C variables anywhere ex. at function begin.

Development views are evolving also together with the application of scope-based
resource management, aren't they?
https://elixir.bootlin.com/linux/v7.1-rc4/source/include/linux/cleanup.h#L136-L153

Regards,
Markus