[AVR32] NMI debugging

Change the NMI handler to use the die notifier chain to signal anyone
who cares. Add a simple "nmi debugger" which hooks into this chain and
that may dump registers, task state, etc. when it happens.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
diff --git a/include/asm-avr32/irq.h b/include/asm-avr32/irq.h
index 83e6549..9315724 100644
--- a/include/asm-avr32/irq.h
+++ b/include/asm-avr32/irq.h
@@ -11,4 +11,9 @@
 
 #define irq_canonicalize(i)	(i)
 
+#ifndef __ASSEMBLER__
+int nmi_enable(void);
+void nmi_disable(void);
+#endif
+
 #endif /* __ASM_AVR32_IOCTLS_H */