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.

Change-Id: I6a6dcdd6a6bab7d72ddec339f7273e404293ccaf
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>