[L] Change in coreboot[main]: mb/dell: Add OptiPlex 7020/9020 port

[Leah Rowe (Code Review)]

Attention is currently required from: Arthur Heymans, Michael Büchler, Máté Kukri, Nico Huber, ilikenwf, nat ✨.

Leah Rowe has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/55232?usp=email )

Change subject: mb/dell: Add OptiPlex 7020/9020 port
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Patch Set 32:

(1 comment)

Patchset:

PS32: 
i saw that this was +2'd but there are two issues left to investigate: the PWM issue and the IOMMU issue(on graphics cards)

i don't think this should be merged in coreboot until those are corrected - or added as a warning in documentation, as part of this patch, with steps to mitigate (e.g. for PWM use a better/quieter fan with adapter and cut the pwm lines to run it at full speed and/or control it using resistor to run at quieter but otherwise higher speed - mention how to disable IOMMU in coreboot or linux. etc)