Change in coreboot[master]: treewide: Kconfig: replace `def_bool n` by `bool`

[Nico Huber (Code Review)]

Attention is currently required from: Martin Roth, Michael Niewöhner, Werner Zeh.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52809 )

Change subject: treewide: Kconfig: replace `def_bool n` by `bool`
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Patch Set 3:

(1 comment)

Patchset:

PS3:
> It's actually the other way round. Options in `src/mainboards/Kconfig` and below are included before others (soc, drivers, etc.). So, the "first declaration" is the one in the mainboards. Only when a mainboard does not specify a option that has `def_bool` (or `bool; default n`) the soc/driver/... option is used.

I missed that you excluded cases there where the mainboard Kconfig
only specifies a default and no type. Actually, I'm not sure right
now about the subtle differences this makes.