netxen: 128 memory controller support

Future revisions of the chip have 128 bit memory
transactions. Require drivers to implement rmw
in case of sub-128 bit accesses by driver. This
is mostly used by diagnostic tools.

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