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

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Arthur Heymans, Julius Werner, Paul Menzel, Yidi Lin.

Yu-Ping Wu 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 4:

(2 comments)

File src/commonlib/bsd/gcd.c:

https://review.coreboot.org/c/coreboot/+/78798/comment/7f6cce4f_d95aa4b0 :
PS2, Line 10: 	if (a == 0 || b == 0)
> Done.

`gcd(0, 123)` is mathematically well-defined. In addition, if this is taken out, then `gcd(1, 0)` and `gcd(0, 1)` will be different behaviors, which is even more confusing. Therefore I'm fine with adding this back.

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

https://review.coreboot.org/c/coreboot/+/78798/comment/64c88e5a_d9fd9b73 :
PS4, Line 7: {
Add some edge cases here such as

```
gcd32(1, 1);
gcd32(1, 123);
gcd32(123, 1);
gcd32(1, UINT32_MAX);
gcd32(UINT32_MAX, 1);
gcd32(UINT32_MAX, UINT32_MAX);
```