cpu hotplug: s390 doesn't support additional_cpus anymore.

s390 doesn't support the additional_cpus kernel parameter anymore since a
long time.  So we better update the code and documentation to reflect
that.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/cpu-hotplug.txt

@@ -59,15 +59,10 @@ apicid values in those tables for disabled apics. In the event BIOS doesn't
 mark such hot-pluggable cpus as disabled entries, one could use this
 parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
 
-s390 uses the number of cpus it detects at IPL time to also the number of bits
-in cpu_possible_map. If it is desired to add additional cpus at a later time
-the number should be specified using this option or the possible_cpus option.
-
 possible_cpus=n		[s390 only] use this to set hotpluggable cpus.
 			This option sets possible_cpus bits in
 			cpu_possible_map. Thus keeping the numbers of bits set
 			constant even if the machine gets rebooted.
-			This option overrides additional_cpus.
 
 CPU maps and such
 -----------------

kernel/cpu.c

@@ -369,7 +369,7 @@ int __cpuinit cpu_up(unsigned int cpu)
 	if (!cpu_isset(cpu, cpu_possible_map)) {
 		printk(KERN_ERR "can't online cpu %d because it is not "
 			"configured as may-hotadd at boot time\n", cpu);
-#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390)
+#if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
 		printk(KERN_ERR "please check additional_cpus= boot "
 				"parameter\n");
 #endif