rdma: fix max_read_depth_definition.

max_read_depth should be based on max_qp_init_read_atomic, or the
maximum number of read values that the initiator will accept as
outstanding.

The device attributes object contains values for both the initiator
(remote side) and the target (local side). All attributes with the name
init in them are meant to correspond to the initiator. The
qp_read_atomic value represents the number of reads and atomic
operations that can have this device as the target. qp_init_read_atomic
represents how many read operations the initiator has said that we can
have outstanding that have the initiator's rdma device as the target.

Since this number represents how many outstanding reads we will send to
the initiator at once, we should use the qp_init_read_atomic value.

Change-Id: Iacc044e8321080de8accd9128ac3777bbb948afc
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/c/442409


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>