netxen: remove unnecessary structures

Remove unnecessary offsetof calulations on these structures:
netxen_board_info, netxen_user_old_info, netxen_new_user_info.

The offsets into the flash are fixed, don't need to be calculated.

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