dwmw2: Tidy up a little, simpler matching on which GPIO is being accessed,
       only register on newer boards, register under PCI device instead of
       duplicating them under each ATM device.
Signed-off-by: Nathan Williams <nathan@traverse.com.au>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>