EDAC/amd64: Split get_csrow_nr_pages() into dct/umc functions

Split get_csrow_nr_pages() into a legacy and modern versions in preparation
for further legacy/modern refactoring.

Also, rename f17_get_cs_mode() to match the new convention.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230127170419.1824692-8-yazen.ghannam@amd.com