Change in coreboot[master]: option: Add API for mainboard provided options

[Nico Huber (Code Review)]

Attention is currently required from: Bill XIE, Patrick Rudolph, Christian Walter, Julius Werner, Kyösti Mälkki.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52601 )

Change subject: option: Add API for mainboard provided options
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Patch Set 1:

(1 comment)

Patchset:

PS1: 
I think this is not a bad idea in general, but it doesn't seem like
what is needed in the follow up. If the board isn't using the CMOS
option table (I've not found any cmos.layout), it would not need
arbitration between the two option backends. Instead we could have
a single active backend (decided at compile time) and that it is
called is simply decided by what files are included into the build.
Just a thought, it wouldn't need this if (CONFIG(X)) call x, else if...