Wake On Lan was not working on laptop DELL Vostro 1500.
If WOL was turned on, BCM4401 was powered up in suspend mode. LEDs blinked.
But the laptop could not be woken up with the Magic Packet. The reason for
that was that PCIE was not enabled as a system wakeup source and
therefore the host PCI bridge was not powered up in suspend mode.
PCIE was not enabled in suspend by PM because no child devices were
registered as wakeup source during suspend process.
On laptop BCM4401 is connected through the SSB bus, that is connected to the
PCI-Express bus. SSB and B44 did not use standard PM wakeup functions
and did not forward wakeup settings to their parents.
To fix that B44 driver enables PM wakeup and registers new wakeup source
using device_set_wakeup_enable(). Wakeup is automatically reported to the parent SSB
bus via power.wakeup_path. SSB bus enables wakeup for the parent PCI bridge, if there is any
child devices with enabled wakeup functionality. All other steps are
done by PM core code.

Signed-off-by: Andrey Skvortsov <Andrej.Skvortzov@gmail.com>
Signed-off-by: Michael Buesch <m@bues.ch>
Signed-off-by: John W. Linville <linville@tuxdriver.com>