netxen: add sysfs entries for diag tools

Add sysfs entries to enable register and memory access
for diagnostic 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>