x86, ds, bts: cleanup/fix DS configuration

Cleanup the cpuid check for DS configuration.

This also fixes a Corei7 CPUID enumeration bug.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>