staging: ks7010: remove cast from netdev_priv()

The returned pointer from netdev_priv() (void *) does not need to be
cast.

Remove unnecessary cast of void * returned by netdev_priv().
Signed-off-by: NTobin C. Harding <me@tobin.cc>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>