x86/CPU/AMD: Move the Zen3 BTC_NO detection to the Zen3 init function

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: http://lore.kernel.org/r/20231120104152.13740-4-bp@alien8.de