[XS] Change in coreboot[main]: stddef.h: Introduce nullptr constant

[Elyes Haouas (Code Review)]

Attention is currently required from: Felix Singer, Jakub Czapiga, Martin L Roth, Nico Huber.

Elyes Haouas has posted comments on this change by Elyes Haouas. ( https://review.coreboot.org/c/coreboot/+/83459?usp=email )

Change subject: stddef.h: Introduce nullptr constant
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Patch Set 26:

(1 comment)

File src/include/stddef.h:

https://review.coreboot.org/c/coreboot/+/83459/comment/dfc1a64b_9dbb1550?usp... :
PS26, Line 25: #define nullptr ((void *)0)
> Just checking, I thought we decided against using `nullptr`/`nullptr_t` in […]

By my understanding, leadership is against changing `NULL` by `nullptr` and not using new constants that modern C provides.
This allow using new "functionality" without changing old coding style for null pointer.