MFC r212755:

MFC r212755:
  Fix incorrect RX BD producer updates. The producer index was
  already updated after allocating mbuf so driver had to use the last
  index instead of using next producer index. This should fix driver
  hang which may happen under high network load.

  Reported by:	Igor Sysoev <is <> rambler-co dot ru>, Vlad Galu <dudu <> dudu dot ro>
  Tested by:	Igor Sysoev <is <> rambler-co dot ru>, Vlad Galu <dudu <> dudu dot ro>

git-svn-id: svn://svn.freebsd.org/base/stable/8@213208 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f