netxen: sysfs control for auto firmware recovery

Firmware hang detection and recovery (reset) need to
be disabled for diagnostic tools, which can run
some disruptive tests.

This adds a driver level control to turn off this
feature by diag tools.

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