lscpu: cleanup DMI detection return codes

lscpu: cleanup DMI detection return codes

Michal wrote:
 There is weird mix of logic in lscpu-dmi.c which sometimes returns 0 and
 sometimes -1 on error. Since most checks are if (rc) goto done; this
 bails out early on error skipping some detection methods. Further, in
 lscpu.c all following detections are guarder by if(hyper) so returning
 -1 causes all following methods to be skipped.

Reported-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>