[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/kdebug.h b/include/asm-avr32/kdebug.h
index fd7e990..ca4f954 100644
--- a/include/asm-avr32/kdebug.h
+++ b/include/asm-avr32/kdebug.h
@@ -5,6 +5,7 @@
 enum die_val {
 	DIE_BREAKPOINT,
 	DIE_SSTEP,
+	DIE_NMI,
 };
 
 #endif /* __ASM_AVR32_KDEBUG_H */