ARM: fix "bad mode in ... handler" message for undefined instructions

The array was missing the final entry for the undefined instruction
exception handler; this commit adds it.

Cc: <stable@vger.kernel.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/traps.c

@@ -36,7 +36,13 @@
 #include <asm/system_misc.h>
 #include <asm/opcodes.h>
 
-static const char *handler[]= { "prefetch abort", "data abort", "address exception", "interrupt" };
+static const char *handler[]= {
+	"prefetch abort",
+	"data abort",
+	"address exception",
+	"interrupt",
+	"undefined instruction",
+};
 
 void *vectors_page;