bnx2x: Fix chip hanging due to TX pipe stall.

bnx2x: Fix chip hanging due to TX pipe stall.

Fix a problem in which the 578xx chip hangs after running traffic, and then pulling the network cable.
This occurs since TX pipe is stalled due to missing XON indication towards the NIG.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit b507766205f85d6d69892287e346a7c264a216b4)

Signed-off-by: Joe Jin <joe.jin@oracle.com>