Staging: w35und: remove ->shutdown from struct wbsoft_priv

It's not actually used for anything, so remove it.

Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>