RDMA/cxgb4: Only log rx_data warnings if cpl status is non-zero

With newer firmware, we can get streaming data due to connection
errors before the driver moves the QP out of RTS.

Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>