PCI: Allow manual resource allocation for PCI hotplug bridges

At the moment only PCI-E briges can be flagged as hotplug, thus
allowing manual resource preallocation via pci=hpmemsize=nnM and
pci=hpiosize=nnM kernel parameters. Some PCI hotplug bridges, e.g.
PLX 6254 can also benefit from this functionalily, as kernel fails
to properly allocate their resources when hotplug device is added
and PCI bus is rescanned.

This patch adds header quirk for PLX 6254 that marks this bridge
as hotplug. Other PCI bridges with similar problems can use it
as well.

Signed-off-by: Felix Radensky <felix@embedded-sol.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>