x86, voyager: fix smp_intr_init() compile breakage

Impact: fix x86/Voyager build

Looks like this became static on the rest of x86.  Fix it up by adding
an external definition to mach-voyager/setup.c

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/voyager.h b/arch/x86/include/asm/voyager.h
index 9c811d2..b3e6473 100644
--- a/arch/x86/include/asm/voyager.h
+++ b/arch/x86/include/asm/voyager.h
@@ -520,6 +520,7 @@
 extern void voyager_cat_power_off(void);
 extern void voyager_cat_do_common_interrupt(void);
 extern void voyager_handle_nmi(void);
+extern void voyager_smp_intr_init(void);
 /* Commands for the following are */
 #define	VOYAGER_PSI_READ	0
 #define VOYAGER_PSI_WRITE	1