pci: pci-uclass: Add VF BAR map support for Enhanced Allocation

Makes dm_pci_map_bar API available to map BAR for Virtual function
PCI devices which support Enhanced Allocation.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>