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

Call them from their respective hw_info_get() function. Avoid the
need for family/model-based function pointers.

Add the calls before reading hardware registers from the memory
controllers, since the number of chip select bases and masks needs to be
known first.

  [ Yazen: rebased/reworked patch and reworded commit message. ]

Signed-off-by: Muralidhara M K <muralidhara.mk@amd.com>
Co-developed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
Signed-off-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
Co-developed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230127170419.1824692-13-yazen.ghannam@amd.com