There was an off-by-1 in the qcode conversion array bounds
check.
Fixes: e709a61a8fe1076a487376fd657544418a38ba06
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>