netxen: use module parameter correctly

Netxen driver is doing this bogus thing to create a control file.
This fails if device doesn't exist, and overall is a bad way to do
the module parameter. Rather than fix borked code, just rewrite.
Just using a writeable module parameter of 0/1 is the correct way

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>