Change in coreboot[master]: lib: Add a mutex

[Kyösti Mälkki (Code Review)]

Attention is currently required from: Raul Rangel, Nico Huber, Xiang W, Philipp Hug, Jonathan Neuschäfer, Tim Wawrzynczak, Angel Pons, Rob Barnes, Karthik Ramasubramanian.
Kyösti Mälkki has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/59320 )

Change subject: lib: Add a mutex
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Patch Set 15:

(1 comment)

Patchset:

PS15:
> > All this review is happening in a no-op change, while CB:59321 is where spinlock/mutex change real […]

You can have your size comparison of the two approaches, but for that I need a commit hash for Raul's work rebased on master. I anticipate PCI IO config to blow if we make it SMP safe with mutex.

I have still not seen comments or numbers what happens to DMA performance if console loglevel changes or UART8250MEM has not been selected.