ASPM issues may result in the NIC not being accessible any longer.
In this case disabling ASPM may not work. Therefore detect this case
by checking whether register reads return ~0, and try to make the
NIC accessible again by resetting the secondary bus.

v2:
- add exception handling for the case that pci_reset_bus() fails
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>