rds: rdma: update rdma transport for tos

For RDMA transports, RDS TOS is an extension of IB QoS(Annex A13)
to provide clients the ability to segregate traffic flows for
different type of data. RDMA CM abstract it for ULPs using
rdma_set_service_type(). Internally, each traffic flow is
represented by a connection with all of its independent resources
like that of a normal connection, and is differentiated by
service type. In other words, there can be multiple qp connections
between an IP pair and each supports a unique service type.

The feature has been added from RDSv4.1 onwards and supports
rolling upgrades. RDMA connection metadata also carries the tos
information to set up SL on end to end context. The original
code was developed by Bang Nguyen in downstream kernel back in
2.6.32 kernel days and it has evolved over period of time.

Reviewed-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
[yanjun.zhu@oracle.com: Adapted original patch with ipv6 changes]
Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>