Pull up following revision(s) (requested by msaitoh in ticket #816):

sys/dev/pci/if_wm.c: revision 1.578

  Fix a bug that TX might stall because WM_TXQ_NO_SPACE is not cleared in
if_init() (though I've never seen this problem). Clear txq->txq_flags in
wm_init_tx_queue(). OK'd by knakahara.

(martin)