irq_pipeline: likely/unlikely macro usage

Hi all,

while staring at the irq_pipelining implementation, I noticed that there
are some locations that use the unlikely macro for the OOB fast path,
e.g., [1].

Could someone explain why we are optimizing for the in-band path here?
Although the in-band path is indeed more likely, I would have expected
that we would want to optimize for the OOB path anyway, since this is
where the saved cycles really matter.

Best,
Tobias

[1] 
https://gitlab.com/Xenomai/linux-dovetail/-/blob/v5.10.y-dovetail/arch/x86/kernel/irq_pipeline.c?ref_type=heads#L260