Refine check on bkpt so that smc and undefined instruction encodings are
handled as an undefined instruction and trap.
Signed-off-by: NAdam Lackorzynski <adam@os.inf.tu-dresden.de>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NNathan Froyd <froydnj@codesourcery.com>