rx: Reorganise transmit queue walk

rx: Reorganise transmit queue walk

The transmit queue is stored in the order that we transmitted the
packets (by sequence number). This means that we can do all of the
ACK processing by just doing a single walk of this queue, rather
than having to walk the queue multiple times, once for each type of
ACK.

This clarifies the queue processing, and should reduce the amount of
time that we spending iterating large transmit queues.

(cherry picked from commit fe7d38f3205bd879e961f5849ed64df5b495388a)
Reviewed-on: http://gerrit.openafs.org/4796
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Change-Id: I85dd1d1706227599a48c7f75ca1947af0b5184bf
Reviewed-on: http://gerrit.openafs.org/4915
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>