x86/amd_nb: Simplify function 3 search

Use the newly introduced helper function to look up "function 3". Drop
unused PCI IDs and code.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250107222847.3300430-8-yazen.ghannam@amd.com