IB/hfi1: Remove cache and embed txreq in ring

This patch removes kmem cache allocation and deallocation in favor of
having the ipoib_txreq in the ring.

The consumer is now the packet sending side allocating tx descriptors from
ring and the producer is the napi interrupt handling freeing tx
descriptors.

The locks are now eliminated because the napi tx lock insures a single
consumer and the napi handling insures a single producer.

The napi poll is converted to memory poll looking for items that have been
marked completed.

Fixes: d99dc602 ("IB/hfi1: Add functions to transmit datagram ipoib packets")
Link: https://lore.kernel.org/r/20210913132826.131370.4397.stgit@awfm-01.cornelisnetworks.com


Signed-off-by: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>