x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU hotplug operations

Without this fix, /proc/cpuinfo will display an incorrect amount
of CPU cores, after bringing them offline and online again, as
exemplified below:

  $ cat /proc/cpuinfo | grep cores
  cpu cores	: 4
  cpu cores	: 8
  cpu cores	: 8
  cpu cores	: 20
  cpu cores	: 4
  cpu cores	: 3
  cpu cores	: 2
  cpu cores	: 2

This patch fixes this by always zeroing the booted_cores variable
upon turning off a logical CPU.

Tested-by: Dou Liyang <[email protected]>
Signed-off-by: Samuel Neves <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: sneves

arch/x86/kernel/smpboot.c

@@ -1437,6 +1437,7 @@ static void remove_siblinginfo(int cpu)
 	cpumask_clear(topology_sibling_cpumask(cpu));
 	cpumask_clear(topology_core_cpumask(cpu));
 	c->cpu_core_id = 0;
+	c->booted_cores = 0;
 	cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);
 	recompute_smt_state();
 }