[netdrvr] forcedeth: Restore multicast settings on resume

nv_open() resets multicast settings, call nv_set_multicast(dev)
to restore them.  (Maybe this should rather be moved into nv_open())

Signed-off-by: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>