i386: Add new property to control cache info

The property legacy-cache will be used to control the cache information.
If user passes "-cpu legacy-cache" then older information will
be displayed even if the hardware supports new information. Otherwise
use the statically loaded cache definitions if available.

Renamed the previous cache structures to legacy_*. If there is any change in
the cache information, then it needs to be initialized in builtin_x86_defs.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Tested-by: Geoffrey McRae <geoff@hostfission.com>
Message-Id: <20180514164156.27034-3-babu.moger@amd.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>