IPoIB: Skip IBoE ports

IPoIB is IP-over-Infiniband link layer. In the case of IBoE, the link
layer is Ethernet and IP can work directly over Ethernet, so disable
IPoIB for non-IB_LINK_LAYER_INFINIBAND ports.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>