PCI: endpoint: Simplify epc->ops->set_bar()/pci_epc_set_bar()

Add barno and flags to struct epf_bar.
That way we can simplify epc->ops->set_bar()/pci_epc_set_bar()
by passing a struct *epf_bar instead of a whole lot of arguments.

This is needed so that epc->ops->set_bar() implementations can
modify BAR flags. Will be utilized in a succeeding patch.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>