MFC r213423:

MFC r213423:
  Move updating TX packet counter to the inside of send loop. axe(4)
  controllers combine multiple TX requests into single one if there
  is room in TX buffer of controller. Updating TX packet counter at
  the end of TX completion resulted in incorrect TX packet counter as
  axe(4) thought it sent 1 packet. There is no easy way to know how
  many combined TX were completed in the callback.
  Because this change updates TX packet counter before actual
  transmission, it may not be ideal one. But I believe it's better
  than showing fake 8kpps under high TX load. With this change, TX
  shows 221kpps on Linksus USB200M.

git-svn-id: svn://svn.freebsd.org/base/stable/8@214297 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f