staging: r8712u: Interface-state not fully tracked.

padapter->bup is True when the interface has been
brought Up. But it was not being reset when the
interface is taken Down.
This has not caused a known problem, as other
state variables may be compensating for it. Never
the less, it is now properly tracked.

Signed-off-by: Ali Bahar <ali@internetDog.org>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>