netxen: fix deadlock on dev close

netxen: fix deadlock on dev close

The tx ring accounting fix in commit cb2107be


("netxen: fix tx ring accounting") introduced intermittent
deadlock when inteface is going down.

This was possibly combined effect of speculative tx pause,
calling netif_tx_lock instead of queue lock and unclean
synchronization with napi which could end up unmasking
interrupt.

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>