fix of osmoload, flashing c155 works

[Andreas Eversberg]

Sylvain Munaut wrote:
>   - I'm not sure it's the correct way to fix it. Having mgb_pull return
> a pointer to the end of the bytes we just removed seems a very weird
> API ... maybe the bug is msgb_pull itself.
for all msgb_pull_u* harald took this into account, so i think there is 
a reason for that. but i don't like this way either.
>   - The addition of the handler for KEY_MENU should be a separate
> patch, not in that one.
again i missed to remove that when creating diffs...