USB: skip Set-Interface(0) if already in altsetting 0

USB: skip Set-Interface(0) if already in altsetting 0

When a driver unbinds from an interface, usbcore always sends a
Set-Interface request to reinstall altsetting 0.  Unforunately, quite
a few devices have buggy firmware that crashes when it receives this
request.

To avoid such problems, this patch (as1180) arranges to send the
Set-Interface request only when the interface is not already in
altsetting 0.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>