Change in coreboot[master]: [WIP,RFC] Clean up spinlocks

[Raul Rangel (Code Review)]

Attention is currently required from: Jason Glenesk, Marshall Dawson, Tim Wawrzynczak, Julius Werner, Kyösti Mälkki, Karthikeyan Ramasubramanian, Felix Held.
Raul Rangel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/59094 )

Change subject: [WIP,RFC] Clean up spinlocks
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Patch Set 2:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/59094/comment/92b06678_ba9d973e 
PS2, Line 14: IMO commit a98d302fe9 x86/smp/spinlock: Disable thread coop when taking spinlock
            : is wrong and should be reverted too.
> > I think there is a disconnect between spinlock and thread_mutex. […]

Honestly, thinking about this more... I think we just delete spin_lock and replace it with a multi cpu aware mutex. I think it makes the whole thing cleaner and less confusing. When thread coop is enabled, we can yield, when it's disabled, we just spin in a busy loop.

I think we should get this patch landed in the mean time. Can  you clean up the commit message?