x86/voyager: fix compile breakage casued by x86: move prefill_possible_map calling early

Impact: fix build failure on x86/Voyager

Before:

| commit 329513a3
| Author: Yinghai Lu <yhlu.kernel@gmail.com>
| Date:   Wed Jul 2 18:54:40 2008 -0700
|
|     x86: move prefill_possible_map calling early

prefill_possible_mask() was hidden under CONFIG_HOTPLUG_CPU rendering
it invisitble to voyager.  Since this commit it's exposed, but not
provided by the voyager subarch, so add a dummy stub to fix the link
breakage.
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/mach-voyager/voyager_smp.c

@@ -345,6 +345,12 @@ static void do_quad_bootstrap(void)
 	}
 }
 
+void prefill_possible_map(void)
+{
+	/* This is empty on voyager because we need a much
+	 * earlier detection which is done in find_smp_config */
+}
+
 /* Set up all the basic stuff: read the SMP config and make all the
  * SMP information reflect only the boot cpu.  All others will be
  * brought on-line later. */