[S] Change in coreboot[main]: nb/intel/sandybridge/raminit: Set MR2 on per DIMM basis

[Angel Pons (Code Review)]

Attention is currently required from: Patrick Rudolph.

Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79783?usp=email )

Change subject: nb/intel/sandybridge/raminit: Set MR2 on per DIMM basis
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Patch Set 3:

(2 comments)

File src/northbridge/intel/sandybridge/raminit_common.c:

https://review.coreboot.org/c/coreboot/+/79783/comment/b77d3cad_981550f8 :
PS3, Line 781: rank/2
nit: spacing around `/`
Also, for readability, an auxiliary constant would help:

```c
const int slot = rank / 2;
```

https://review.coreboot.org/c/coreboot/+/79783/comment/f06e4676_d9a48b18 :
PS3, Line 799: 	reg32 &= 1 << (rank / 2 + 14) | 1 << (rank / 2 + 6);
I don't think this should be changed. The code reads the MR2 shadow register, keeps the values of the other slot's bits, combines this with the MR2 contents, then adds the slot-specific bits, and finally writes back the updated value.

Right now, this would result in the bits for the first rank being cleared, which is bad (test with a DIMM that uses address mirroring on the first slot, and any other DIMM in the second slot of the same channel)