Change in coreboot[master]: soc/amd/picasso/psp: move to common code and rename to psp_smm_gen2

[Marshall Dawson (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Martin Roth, Felix Held.
Marshall Dawson has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50515 )

Change subject: soc/amd/picasso/psp: move to common code and rename to psp_smm_gen2
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Patch Set 2: Code-Review+2

(1 comment)

Patchset:

PS2: 
I think I've expressed reservations elsewhere about moving SMIxnnn registers to common, i.e. someday we may find they're not as common as we expected so additional work will be required.  For this patch we're using a couple of named registers in that space (OK) but also bit definitions at the top of SMITRG0.  However, those have seemed to stay unchanged across products.