[ARM] Fix SMP initialisation oops

A change to the SMP initialisation caused the following oops:

 CPU1: Booted secondary processor
 CPU1: D VIPT write-back cache
 CPU1: I cache: 32768 bytes, associativity 4, 32 byte lines, 256 sets
 CPU1: D cache: 32768 bytes, associativity 4, 32 byte lines, 256 sets
 <7>Calibrating delay loop... 83.14 BogoMIPS (lpj=415744)
 <1>Unable to handle kernel NULL pointer dereference at virtual address 0000001c
 ...
 PC is at enqueue_task+0x1c/0x64
 LR is at activate_task+0xcc/0xe4

SMP initialisation now requires cpu_possible_map to be initialised in
setup_arch().  Move this from smp_prepare_cpus() to smp_init_cpus()
and call it from our setup_arch() if CONFIG_SMP is enabled.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/setup.c

@@ -23,6 +23,7 @@
 #include <linux/root_dev.h>
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
+#include <linux/smp.h>
 
 #include <asm/cpu.h>
 #include <asm/elf.h>
@@ -771,6 +772,10 @@ void __init setup_arch(char **cmdline_p)
 	paging_init(&meminfo, mdesc);
 	request_standard_resources(&meminfo, mdesc);
 
+#ifdef CONFIG_SMP
+	smp_init_cpus();
+#endif
+
 	cpu_init();
 
 	/*

arch/arm/kernel/smp.c

@@ -338,7 +338,6 @@ void __init smp_prepare_boot_cpu(void)
 
 	per_cpu(cpu_data, cpu).idle = current;
 
-	cpu_set(cpu, cpu_possible_map);
 	cpu_set(cpu, cpu_present_map);
 	cpu_set(cpu, cpu_online_map);
 }