i386: host_vendor_fms() helper function

Helper function for code that needs to check the host CPU
vendor/family/model/stepping values.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20170309181212.18864-2-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
