x86, ds: selftest each cpu

Perform debug store selftests on each cpu.

Cover both the normal and the _noirq variant of the debug store interface.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144559.394583000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>