Change in coreboot[master]: cpu/x86/lapic: Fix choice X2APIC_ONLY

[Kyösti Mälkki (Code Review)]

Attention is currently required from: Nico Huber, Wonkyu Kim, Tim Wawrzynczak, Angel Pons.
Kyösti Mälkki has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/60213 )

Change subject: cpu/x86/lapic: Fix choice X2APIC_ONLY
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Patch Set 3:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/60213/comment/56fd5f27_4a43e2a8 
PS2, Line 11: avoid entering a printk() and acquiring console_lock and
            : dead-locking.
> `mfence; lfence` […]

The ones Angel referred to in linux kernel seem to serve different purpose; the fence are inserted prior to the IPI? I think that is required for the raised interrupt service to not fetch stale data from memory?

I can test on a intel/denverton platform, maybe this weekend.