Since IB/core resolves the destination mac address for user and kernel
consumers, avoid resolving in multiple provider drivers.

Only ib_core resolves DMAC now, therefore resolve_eth_dmac is removed as
exported symbol.
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NLeon Romanovsky <leon@kernel.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>