In general a BIOS may goof or we may hotplug in a hotplug controller.
In either case the kernel needs to reserve resources for plugging
in more devices in the future instead of creating a minimal resource
assignment.

We already do this for cardbus bridges I am just adding a variant
for pcie bridges.

v2: Make testing for pcie hotplug bridges based on a flag.

    So far we only set the flag for pcie but a header_quirk
    could easily be added for the non-standard pci hotplug
    bridges.
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>