net/rds: Add per cp work queue

net/rds: Add per cp work queue

This patch adds a per connection workqueue which can be initialized
and used independently of the globally shared rds_wq.

This patch is the first in a series that aims to address tcp ack
timeouts during the tcp socket shutdown sequence.

This initial refactoring lays the ground work needed to alleviate
queue congestion during heavy reads and writes.  The independently
managed queues will allow shutdowns and reconnects respond more quickly
before the peer(s) timeout waiting for the proper acks.

Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Link: https://patch.msgid.link/20260109224843.128076-2-achender@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>