PCI: endpoint: Create configfs entry for each pci_epf_device_id table entry

In order to be able to provide correct driver_data for pci_epf device,
a separate configfs entry for each pci_epf_device_id table entry in
pci_epf_driver is required.

Add support to create configfs entry for each pci_epf_device_id
table entry here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>