PCI: conditional resource-reallocation through kernel parameter pci=realloc

Multiple attempts to dynamically reallocate pci resources have
unfortunately lead to regressions. Though we continue to fix the
regressions and fine tune the dynamic-reallocation behavior, we have not
reached a acceptable state yet.

This patch provides a interim solution. It disables dynamic reallocation
by default, but adds the ability to enable it through pci=realloc kernel
command line parameter.

Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>