IB/ib_mthca: Pre-link receive WQEs in Tavor mode

We have recently discovered that Tavor mode requires each WQE in a
posted list of receive WQEs to have a valid NDA field at all times.
This requirement holds true for regular QPs as well as for SRQs.  This
patch prelinks the receive queue in a regular QP and keeps the free
list in SRQ always properly linked.

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