NR_CPUS: Replace NR_CPUS in arch/x86/kernel/cpu/mcheck/mce_64.c

  * nr_cpu_ids should be used to allocate arrays based on the number of
    cpu's present.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>