My experiences tend to suggest that when the submit button doesn't show up even when you put the code for it (well, sometimes one can simply forget...) it is usually because there is a problem with the entity definition or setter definition. Since you have an entity that is in one to one correspondence with another entity, sometimes defining setter can get tricky.
Otherwise, in your attached code, I see
Code:
namespace XLite\Module\<dev>\<dev>\Controller\Admin;
in the class Controller/Admin/MlBanner.php (where it should be <dev>/<mod>, but I would presume the error was made while you replaced real developer name and module name with <dev> and <mod>?