x86, cacheinfo: Unify AMD L3 cache index disable checking

All F10h CPUs starting with model 8 resp. 9, stepping 1, support L3
cache index disable. Concentrate the family, model, stepping checking at
one place and enable the feature implicitly on upcoming Fam10h models.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <1271945222-5283-2-git-send-email-bp@amd64.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>