PCI: designware-ep: Allow pci_epc_set_bar() update inbound map address

ntb_mw_set_trans() will set memory map window after endpoint function
driver bind. The inbound map address need be updated dynamically when
using NTB by PCIe Root Port and PCIe Endpoint connection.

Checking if iatu already assigned to the BAR, if yes, using assigned iatu
number to update inbound address map and skip set BAR's register.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>