IB/isert: use new shared CQ mechanism

Have the driver use shared CQs provided by the rdma core driver.  Since
this provides similar functionality to iser_comp it has been removed.

Now there is no reason to allocate very large CQs when the driver is
loaded while gaining the advantage of shared CQs. Previously when a single
connection was opened a CQ was opened for every core with enough space for
eight connections, this is a very large overhead that in most cases will
not be utilized.

Link: https://lore.kernel.org/r/20200722135629.49467-2-maxg@mellanox.com


Signed-off-by: Yamin Friedman <yaminf@mellanox.com>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>