ipg: fix receivemode IPG_RM_RECEIVEMULTICAST{,HASH} in ipg_nic_set_multicast_list()

The branches are dead code.  even when dev->flag IFF_MULTICAST (defined
0x1000) is set, dev->flags & IFF_MULTICAST & [boolean] always evaluates to
0.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Francois Romieu <romieu@fr.zoreil.com>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>