simplify the logic of pm id image loading

[leejet]

No description provided.

[wbruna]

@leejet , the help text mentions the normalize_input flag is part of Photomaker functionality (and in that case it should probably be moved inside the sd_pm_params_t struct). But the generate_image_internal function doesn't seem to do anything with it?

[leejet]

For the original version of Photomaker, normalization is necessary. The normalize_input parameter will be removed later.