x86/CPU/AMD: Move Zenbleed check to the Zen2 init function

Prefix it properly so that it is clear which generation it is dealing
with.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: http://lore.kernel.org/r/20231120104152.13740-8-bp@alien8.de