mlx4_core: Implement SRQ object lookup from srqn

Expose a new API mlx4_srq_lookup() to retrive a SRQ based on its
number. This API is needed in the mlx4_ib driver CQ polling logic,
when a work completion is associated with a XRC TGT QP. Since a
target QP may redirect to more than one XRC SRQ, the srq field in the
QP has no usage and the real XRC SRQ need to be retrived using the
information from the XRCETH IB header which is placed in the HW CQE.

Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

IB/mlx4: Add a driver Mellanox ConnectX InfiniBand adapters

Add an InfiniBand driver for Mellanox ConnectX adapters. Because
these adapters can also be used as ethernet NICs and Fibre Channel
HBAs, the driver is split into two modules:

mlx4_core: Handles low-level things like device initialization and
processing firmware commands. Also controls resource allocation
so that the InfiniBand, ethernet and FC functions can share a
device without stepping on each other.

mlx4_ib: Handles InfiniBand-specific things; plugs into the
InfiniBand midlayer.

Signed-off-by: Roland Dreier <rolandd@cisco.com>