Change in coreboot[master]: mb/purism/librem_mini: Drop superfluous devices from devicetree

[Nico Huber (Code Review)]

Attention is currently required from:  Felix Singer, Furquan Shaikh, Matt DeVillier, Tim Wawrzynczak, Angel Pons, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/51663 )

Change subject: mb/purism/librem_mini: Drop superfluous devices from devicetree
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Patch Set 2:

(1 comment)

Patchset:

PS2: 
The `.on_mainboard` field of `struct device` would be wrong.

It's hard to get right, though, if you need to attach a "chip"
driver to something in a slot (we'd have a false positive
`.on_mainboard = 1`). But that's a deficiency of the drivers
that pretend to be chip drivers but aren't.