Mark RDSv3.1 as compat version and add v4.1 version macro's.
Subsequent patches enable TOS(Type of Service) feature which is
tied with v4.1 for RDMA transport.

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>