Change in coreboot[master]: src: use ARRAY_SIZE where possible

[Patrick Georgi (Code Review)]

Attention is currently required from: Michał Żygowski, Mariusz Szafrański, Suresh Bellampalli, Vanessa Eusebio, Angel Pons, Michal Motyl, Werner Zeh, Patrick Rudolph, Piotr Król, HAOUAS Elyes.
Patrick Georgi has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50594 )

Change subject: src: use ARRAY_SIZE where possible
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Patch Set 3:

(1 comment)

File src/northbridge/intel/ironlake/raminit.c:

https://review.coreboot.org/c/coreboot/+/50594/comment/e4848f2a_b0cf23d9 
PS2, Line 3773: 				     ARRAY_SIZE(useful_addresses); addr++)
> The whole file is a mess. I'd rather fix the coding style in a follow-up. […]

There are a few more instances of this now, but I'm not too concerned due to https://review.coreboot.org/q/topic:%22clang-format-all-the-things%22+(statu...)

(This issue came to my attention during work on that topic)