PCI: endpoint: Add support to handle multiple base for mapping outbound memory

PCI: endpoint: Add support to handle multiple base for mapping outbound memory

R-Car PCIe controller has support to map multiple memory regions for
mapping the outbound memory in local system also the controller limits
single allocation for each region (that is, once a chunk is used from the
region it cannot be used to allocate a new one). This features inspires to
add support for handling multiple memory bases in endpoint framework.

With this patch pci_epc_mem_init() initializes address space for endpoint
controller which support single window and pci_epc_multi_mem_init()
initializes multiple windows supported by endpoint controller.

Link: https://lore.kernel.org/r/1588854799-13710-6-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>