sb_edac: make memory type detection per memory controller

Haswell has different register, offset to determine memory type and supports
DDR4 in some models. This patch makes it easier to have a different method
depending on the memory controller type.

Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>