Change in coreboot[master]: broadwell boards: Do not set `ddr_refresh_2x` again

[Patrick Georgi (Code Review)]

Attention is currently required from: Nico Huber, Matt DeVillier, Angel Pons, Arthur Heymans, Patrick Rudolph.
Patrick Georgi has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/55810 )

Change subject: broadwell boards: Do not set `ddr_refresh_2x` again
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Patch Set 9:

(1 comment)

File src/mainboard/google/auron/variants/buddy/spd/spd.c:

https://review.coreboot.org/c/coreboot/+/55810/comment/5d64e447_1a2b1642 
PS9, Line 13: 	pei_data->ddr_refresh_2x = 1;
ddr_refresh_2x is a rowhammer mitigation. We had some complications with updating stuff in the field: I think back then, romstage was part of the RO partition and so there had been workarounds (e.g. boot, set the flag, force a resume cycle to reinit RAM into 2x refresh). Could these assignments be related to that?

If so, I'd rather keep them, but amend with a comment that it's for old-RO/new-RW scenarios to ensure that refresh_2x is _really_ used under all circumstances.