sky2: dont enable PME legacy mode

This bit is not changed by vendor driver, and should be left alone.
The documentation implies this a debug bit.
  0 = WAKE# only asserted when VMAIN not available
  1 = WAKE# is depend on wake events and independent of VMAIN.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>