EDAC/amd64: Remove early_channel_count()

The early_channel_count() function seems to have been useful in the past
for knowing how many EDAC mci structures to populate. However, this is no
longer needed as the maximum channel count for a system is used instead.

Remove the early_channel_count() helper functions and related code. Use the
size of the channel layer when iterating over channel structures.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230127170419.1824692-6-yazen.ghannam@amd.com