EOSM: restart the canon dialog for ML menu if it times out

Created originally on Bitbucket by dmilligan (David Milligan)

https://bitbucket.org/hudson/magic-lantern/issues/1974/6d-m-700d-70d-in-live-view-mode-ml-menu

ML on EOSM is almost unusable without this. Ideally we could find and fix the timeout, but at least this works and makes using ML somewhat bearable (lack of buttons still needs to be addressed). I haven't noticed any negative side effects after using this for several weeks. We also can't forego the dialog altogether, lots of screwy things happen if you try.

I don't know if this will work on other cameras, but you're welcome to try it.