x86: remove additional_cpus configurability

additional_cpus=<x> parameter is dangerous and broken: for example
if we boot additional_cpus=-2 on a stock dual-core system it will
crash the box on bootup.

So reduce the maze of code a bit by removingthe user-configurability
angle.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -1438,24 +1438,6 @@ config HOTPLUG_CPU
 	    automatically on SMP systems. )
 	  Say N if you want to disable CPU hotplug.
 
-config HOTPLUG_RESTRICT_TO_BOOTUP_CPUS
-	def_bool n
-	prompt "Restrict CPU hotplugging to processors found during boot" if HOTPLUG_CPU
-	---help---
-	  Say no here to use the default, which allows as many CPUs as are marked
-	  "disabled" by ACPI or MPTABLES to be hotplugged after bootup.
-
-	  Say yes if you do not want to allow CPUs to be added after booting, for
-	  example if you only need CPU hotplugging enabled for suspend/resume.
-
-	  If CPU_HOTPLUG is enabled this value may be overridden at boot time
-	  with the "additional_cpus" kernel parameter.
-
-config HOTPLUG_ADDITIONAL_CPUS
-	int
-	default  0 if !HOTPLUG_CPU || HOTPLUG_RESTRICT_TO_BOOTUP_CPUS
-	default -1
-
 config COMPAT_VDSO
 	def_bool y
 	prompt "Compat VDSO support"

arch/x86/kernel/smpboot.c

@@ -1261,7 +1261,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
 	check_nmi_watchdog();
 }
 
-static int additional_cpus __initdata = CONFIG_HOTPLUG_ADDITIONAL_CPUS;
+static int additional_cpus = -1;
 
 /*
  * cpu_possible_map should be static, it cannot change as cpu's
@@ -1334,12 +1334,6 @@ static void remove_siblinginfo(int cpu)
 	cpu_clear(cpu, cpu_sibling_setup_map);
 }
 
-static __init int setup_additional_cpus(char *s)
-{
-	return s && get_option(&s, &additional_cpus) ? 0 : -EINVAL;
-}
-early_param("additional_cpus", setup_additional_cpus);
-
 static void __ref remove_cpu_from_maps(int cpu)
 {
 	cpu_clear(cpu, cpu_online_map);