[M] Change in coreboot[main]: commonlib: Add GCD function

[Yidi Lin (Code Review)]

Attention is currently required from: Arthur Heymans, Julius Werner, Paul Menzel, Yu-Ping Wu.

Yidi Lin has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78798?usp=email )

Change subject: commonlib: Add GCD function
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Patch Set 5:

(2 comments)

File src/commonlib/bsd/gcd.c:

https://review.coreboot.org/c/coreboot/+/78798/comment/e50b1e54_2535955a :
PS2, Line 10: 	if (a == 0 || b == 0)
> `gcd(0, 123)` is mathematically well-defined. […]

Done

File tests/commonlib/bsd/gcd-test.c:

https://review.coreboot.org/c/coreboot/+/78798/comment/78fbb05c_5309f40a :
PS4, Line 7: {
> Add some edge cases here such as […]

Done