Extend Van Gogh family to include Sephiroth APU Revision.

[jontyab]

Van Gogh functionality appears unchanged in the new Sephiroth APU revision used by Steam Deck Oled.

Specifically tested Curve optimizer (--set-coall) which functions well, and --set-cogfx which continues to be silently accepted by SMU but doesn't appear to do anything, consistent with Aerith behaviour.

[FlyGoat]

LGTM, besides I can't find much information about Sephiroth, do you think we need to define FAM_SEPHIROTH?

[jontyab]

Spent a lunch-hour googling and made little sense of the naming conventions. Aerith/Sephiroth appear to be valve-internal rather than an APU designation from AMD.

While of course the CPUID is self-reporting a distinct model I'd prefer to group them together if they are architecturally identical and 'just a die shrink' but have struggled to find an authoritative source.

Certainly either just FAM_VANGOGH or both FAM_AERITH + FAM_SEPHIROTH
Doesn't seem right to mix VANGOGH and SEPHIROTH

[FlyGoat]

I'm happy with just FAM_VANGOGH then. Will merge.