MFC r212069,212071:

MFC r212069,212071:
r212069:
  bge_txeof() already checks whether it has to free transmitted mbufs
  or not by comparing reported TX consumer index with saved index. So
  remove unnecessary check done after freeing transmitted mbufs.
  While I'm here nuke unnecessary variable initializations.

r212071:
  Remove unnecessary atomic operation in bge_poll. bge(4) always
  holds a driver lock in the function entry and
  memory synchronization is handled by bus_dmamap_sync(9).

git-svn-id: svn://svn.freebsd.org/base/stable/8@213595 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f