netxen: fix tx timeout handling on firmware hang

Clear NX_RESETING bit in netxen_tx_timeout_task() so that
the firmware watchdog task can catch need_reset request
from tx timeout.

Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>