netxen: change firmware write size

Use 8 byte strides for firmware download into card
memory since oncard memory controller needs 8 byte
(64 bit) accesses. This avoids unnecessary rmw cycles.

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>