[PATCH] PCI: make MSI quirk inheritable from the pci bus

It turns out AMD 8131 quirk only affects MSI for devices behind the 8131 bridge.
Handle this by adding a flags field in pci_bus, inherited from parent to child.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>