target/hexagon: add build config for softmmu Reviewed-by: Taylor Simpson <ltaylorsimpson@gmail.com> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Acked-by: Philippe Mathieu-Daudé <philmd@mailo.com> Signed-off-by: Brian Cain <brian.cain@oss.qualcomm.com>