Change in coreboot[master]: commonlib/mem_pool: Allow configuring the alignment

[Raul Rangel (Code Review)]

Attention is currently required from: Furquan Shaikh, Julius Werner, Angel Pons, Karthik Ramasubramanian.
Raul Rangel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56580 )

Change subject: commonlib/mem_pool: Allow configuring the alignment
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Patch Set 11:

(2 comments)

File src/commonlib/include/commonlib/mem_pool.h:

https://review.coreboot.org/c/coreboot/+/56580/comment/b71decfb_646353ec 
PS11, Line 58: alignment
> What is buf % 0?

This will raise a divide by 0 error. Should I add an assert?

File src/commonlib/mem_pool.c:

https://review.coreboot.org/c/coreboot/+/56580/comment/fb531628_6c6af05a 
PS11, Line 11: mp->alignment
> What is the behavior of ALIGN_UP(sz, 0)? Is it defined or undefined?

```
ALIGN_UP(64, 0) => 0x0
```

Should I add an assert, or just return NULL if alignment is 0?