PCI/IOV: Allow drivers to control VF BAR size

PCI/IOV: Allow drivers to control VF BAR size

Drivers could leverage the fact that the VF BAR MMIO reservation is created
for total number of VFs supported by the device by resizing the BAR to
larger size when smaller number of VFs is enabled.

Add pci_iov_vf_bar_set_size() to control the size and a
pci_iov_vf_bar_get_sizes() helper to get the VF BAR sizes that will allow
up to num_vfs to be successfully enabled with the current underlying
reservation size.

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/20250702093522.518099-6-michal.winiarski@intel.com