IB/core: Use GID table in AH creation and dmac resolution

Previously, vlan id and source MAC were used from QP attributes. Since
the net device is now stored in the GID attributes, they could be used
instead of getting this information from the QP attributes.

IB_QP_SMAC, IB_QP_ALT_SMAC, IB_QP_VID and IB_QP_ALT_VID were removed
because there is no known libibverbs that uses them.

This commit also modifies the vendors (mlx4, ocrdma) drivers in order
to use the new approach.

ocrdma driver changes were done by Somnath Kotur <Somnath.Kotur@Avagotech.Com>

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>