This patch adds the following changes into generic PCI code especially
for PCI legacy I/O port free drivers.
- Added new pci_request_selected_regions() and
pci_release_selected_regions() for PCI legacy I/O port free
drivers in order to request/release only the selected regions.
- Added helper routine pci_select_bars() which makes proper mask
of BARs from the specified resource type. This would be very
helpful for users of pci_enable_device_bars().