EDAC/amd64: Do not discover ECC symbol size for Family 17h and later

The ECC symbol size was needed on legacy system to lookup the ECC syndrome.
This is not needed on modern systems because the ECC syndrome is explicitly
provided in the MCA information.

Remove the ECC symbol size discovery code for modern UMC-based systems.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230127170419.1824692-10-yazen.ghannam@amd.com