ionic: pull per-q stats work out of queue loops

Abstract out the per-queue data collection work into separate
functions from the per-queue loops in the stats reporting,
similar to what Alex did for the data label strings in
commit acebe5b6 ("ionic: Update driver to use ethtool_sprintf")

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>