Merge branch 'rds-enable-mprds'

Sowmini Varadhan says:

====================
RDS: TCP: Enable mprds for rds-tcp

The third, and final, installment for mprds-tcp changes.

In Patch 3 of this set, if the transport support t_mp_capable,
we hash outgoing traffic across multiple paths.  Additionally, even if
the transport is MP capable, we may be peering with some node that does
not support mprds, or supports a different number of paths. This
necessitates RDS control plane changes so that both peers agree
on the number of paths to be used for the rds-tcp connection.
Patch 3 implements all these changes, which are documented in patch 5
of the series.

Patch 1 of this series is a bug fix for a race-condition
that has always existed, but is now more easily encountered with mprds.
Patch 2 is code refactoring. Patches 4 and 5 are Documentation updates.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>