netxen : fix debug tools access for NX2031

Driver maps only some part of the MMIO bar 0 in case of
NX2031. This is sufficient for tx and rx by the driver.
When debug tools need to access resources in
unmapped regions, driver needs to map these on the fly
in order to complete read/write request.

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