head.S: move skl_info and bootloader_data fields back

[m-iwanicki]

Fixes issue:

loader/slaunch/skl.c:117:slaunch: Possible SKL module measures bootloader data:
16424 (measured prefix) > 170 (data offset)
error: SKL module isn't correct.

Tested with tb-dev GRUB (meta-trenchboot)

[krystian-hebel]

I think this should be changed on GRUB side instead. The size of soc_flag field is out of our control, and may change without notice. By having skl_info and bootloader_data under known offsets, GRUB won't have to be aware of any changes made by AMD.

[SergiiDmytruk]

I agree that updating this in GRUB a better place in the long run. Can use this modification for testing though since commits are WIP anyway and it should be easier than bumping GRUB.

[krystian-hebel]

By the way, it may be useful to try to change those (presumed) CPUIDs to match the CPU used for testing. I didn't find any documentation as to what those are used by, it may be possible that PSP validates those somehow, but maybe they were meant for whatever loads the binary (GRUB in our case).

[m-iwanicki]

it may be useful to try to change those (presumed) CPUIDs to match the CPU used for testing. I didn't find any documentation as to what those are used by, it may be possible that PSP validates those somehow

Changed when testing on MZ33-AR1 (AMD EPYC 9015). CPUID:

>>> import cpuid
>>> eax, *_ = cpuid.cpuid(1)
>>> f"{eax:#010x}"
'0x00b00f21'

I tested with 0x00b00f20 and 0x00b00f00. Results are the same as in TrenchBoot/trenchboot-issues#79 (comment). Maybe those are validated later if at all.