Add a pci_resize_resource() interface to allow device drivers to resize
BARs of their devices.

This is useful for devices with large local storage, e.g., graphics
devices.  These devices often only expose 256MB BARs initially to be
compatible with 32-bit systems.

This function only tries to reprogram the windows of the bridge directly
above the requesting device and only the BAR of the same type (usually mem,
64bit, prefetchable).  This is done to avoid disturbing other drivers by
changing the BARs of their devices.

Drivers should use the following sequence to resize their BARs:
1. Disable memory decoding of the device using the PCI cfg dword.
2. Use pci_release_resource() to release all BARs which can move during the
   resize, including the one you want to resize.
3. Call pci_resize_resource() for each BAR you want to resize.
4. Call pci_assign_unassigned_bus_resources() to reassign new locations
   for all BARs which are not resized, but could move.
5. If everything worked as expected, enable memory decoding in the device
   again using the PCI cfg dword.

Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>