x86: move prefill_possible_map calling early

call it right after we are done with MADT/mptable handling, instead of
doing that in setup_per_cpu_areas() later on...

this way for_possible_cpu() can be used early.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/setup.c

@@ -818,6 +818,7 @@ void __init setup_arch(char **cmdline_p)
 		get_smp_config();
 #endif
 
+	prefill_possible_map();
 #ifdef CONFIG_X86_64
 	init_cpu_to_node();
 #endif