RDMA/cxgb3: Set the max_qp_init_rd_atom attribute in query_device

The device attribute max_qp_init_rd_atom is not getting set in cxgb3's
query_device method.  Version 1.0.4 of librdmacm now validates the
user's requested initiator and responder resources against the max
supported by the device.  Since iw_cxgb3 wasn't setting this attribute
(and it defaulted to 0), all rdma_connect()s fail if there are
initiator resources requested by the app.  Fix this by setting the
correct value in iwch_query_device().

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>