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/irq.h b/arch/blackfin/include/asm/irq.h
index 89de539..12f4060 100644
--- a/arch/blackfin/include/asm/irq.h
+++ b/arch/blackfin/include/asm/irq.h
@@ -38,4 +38,8 @@
 
 #include <asm-generic/irq.h>
 
+#ifdef CONFIG_NMI_WATCHDOG
+# define ARCH_HAS_NMI_WATCHDOG
+#endif
+
 #endif				/* _BFIN_IRQ_H_ */