tg3: WOL fixes

The first hunk of this patch inverts a flag that was accidentally
toggled as part of commit 0a459aac
("tg3: Allow WOL for phylib controlled Broadcom phys").

The second hunk of the patch removes the call to
device_may_wakeup() in the 5906 config detection path.  At the
point of the call, the driver shouldn't be querying for WOL
capability.  It should be detecting and setting it.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>