For many moons, we've been executing identify_cpu()
on the boot processor twice on SMP kernels.
This is harmless, but has a few downsides..
- Extra cruft in bootlog/dmesg
- Spawns one too many timers for the mcheck handler
- possibly other wasteful things..

This seems to do the right thing here, and has been
acked (after some minor squibbles) on l-k.