Remove the obsolete terse version of do_mii()

We now have more useful version of do_mii() and everybody use it.
Gerald Van Baren says:

> When I originally wrote the mii command 6(!) years ago, I wrote a
> verbose version that printed human readable decomposition of the flags,
> etc., and a terse one that didn't print as much stuff and thus had a
> smaller memory footprint.
>
> It sounds like the terse version has withered and died, apparently
> people are only using the verbose version (which is very understandable,
> I do myself).

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>