netxen: annotate register access functions

o remove unnecessary length parameter since register access
  width is fixed 4 byte.
o remove superfluous pci_read_normalize and pci_write_normalize
  functions.

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