sb_edac: make RIR limit retrieval per model

Haswell has a different way to retrieve RIR limits, make this procedure per
model.

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>