Blackfin: implement nmi_watchdog for SMP on BF561

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/include/asm/smp.h b/arch/blackfin/include/asm/smp.h
index 29fb882..7f26de0 100644
--- a/arch/blackfin/include/asm/smp.h
+++ b/arch/blackfin/include/asm/smp.h
@@ -22,6 +22,7 @@
 struct corelock_slot {
 	int lock;
 };
+extern struct corelock_slot corelock;
 
 void smp_icache_flush_range_others(unsigned long start,
 				   unsigned long end);