RDMA/ocrdma: Add support for IB stack compliant stats in sysfs.

Add the following per-port sysfs traffic counters for RoCE:

        port_xmit_packets
        port_rcv_packets
        port_rcv_data
        port_xmit_data

Signed-off-by: Mitesh Ahuja <mitesh.ahuja@emulex.com>
Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Selvin Xavier <selvin.xavier@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>