x86/apic/es7000+summit: Always make valid apicid from a cpumask

x86/apic/es7000+summit: Always make valid apicid from a cpumask

In case of invalid parameters cpu_mask_to_apicid_and() might
return apicid value of 0 (on Summit) or a uninitialized value
(on ES7000), although it is supposed to return apicid of cpu-0
at least. Fix the operation to always return a valid apicid.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/20120614075026.GH3383@dhcp-26-207.brq.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>