x86, hotplug: Support functions for CPU0 online/offline

Add smp_store_boot_cpu_info() to store cpu info for BSP during boot time.

Now smp_store_cpu_info() stores cpu info for bringing up BSP or AP after
it's offline.

Continue to online CPU0 in native_cpu_up().

Continue to offline CPU0 in native_cpu_disable().

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1352835171-3958-5-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>