[M] Change in coreboot[main]: skl mainboards/dt: Move serirq setting into LPC device scope

[Marvin Evers (Code Review)]

Attention is currently required from: Felix Singer, Frans Hendriks, Jeremy Soller, Jonathon Hall, Michael Niewöhner, Michał Żygowski, Piotr Król, Tim Crawford.

Marvin Evers has posted comments on this change by Felix Singer. ( https://review.coreboot.org/c/coreboot/+/83188?usp=email )

Change subject: skl mainboards/dt: Move serirq setting into LPC device scope
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Patch Set 2: Code-Review+1

(1 comment)

Patchset:

PS2: 
checked whether:

- serirq_mode option has been moved to dt
- all skl/kbl boards are covered