reverse the order of dd arguments to ease copy

reverse the order of dd arguments to ease copy

This is easier to copy-paste:

```
dd bs=4M status=progress conv=fdatasync if=grml_2021.07.iso of=/dev/USB_KEY
```

... because I can just paste it in a terminal and all I have to change is the last word. Compare with the previous version:

```
dd if=grml_2021.07.iso of=/dev/USB_KEY bs=4M status=progress conv=fdatasync
```

... where you have to paste, move your cursor right before ` bs` (notice the space), then change the word.

All that `bs=` and `conv=` is cosmetic anyways, keep the good stuff where it matters, near the end of line, where the cursor will be.