Change in flashrom[master]: layout: Use linked list for `struct romentry`

[Nico Huber (Code Review)]

Attention is currently required from: Edward O'Callaghan, Daniel Campello, Anastasia Klimchuk, Peter Marheine.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/33521 )

Change subject: layout: Use linked list for `struct romentry`
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Patch Set 4:

(2 comments)

File layout.c:

https://review.coreboot.org/c/flashrom/+/33521/comment/64fbbcb2_39035a74 
PS4, Line 369: 	return iterator ? iterator->next : layout->head;
> This duplicates _layout_next. […]

They have different signatures. Let's keep the discussion in CB:33542.

https://review.coreboot.org/c/flashrom/+/33521/comment/0179fbdf_821741f4 
PS4, Line 418: 	entry->next	= layout->head;
> Shouldn't this be NULL? Otherwise it's creating a reference cycle.

No, the current version adds new entries at the list head (if the
list is empty, it sets NULL because `layout->head` is NULL; if not,
the new entry will point to the previous head). That's much more
convenient unless we'd maintain a tail pointer as well. I'd like
to avoid that unless we need to maintain some order of entries.