byte-mem: Improve address selection

[vbmacher]

Loading an image and adding the image in settings have different order of asking for memory address:

• one asks address first, then bank (2 questions)
• another asks bank first, then address (2 questions)

If there is just 1 memory bank (= no "banking"), it asks just for the address.

This is not really UI friendly, the dialog should be unified and optimally just 1 question should be asked.