decodetree: Do not unconditionaly return from Pattern.output_code

decodetree: Do not unconditionaly return from Pattern.output_code

As a consequence, the 'return false' gets pushed up one level.

This will allow us to perform some other action when the
translator returns failure.

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>