pci_ep: add pci endpoint sandbox driver

Add a dummy PCI endpoint for sandbox.
Supporting only a single function, it allows setting
and reading header configuration.

Signed-off-by: Ramon Fried <ramon.fried@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pci_endpoint/Kconfig b/drivers/pci_endpoint/Kconfig
index e00cb75..19cfa0a 100644
--- a/drivers/pci_endpoint/Kconfig
+++ b/drivers/pci_endpoint/Kconfig
@@ -22,4 +22,13 @@
 	  endpoint mode. This PCIe controller may be embedded into many
 	  different vendors SoCs.
 
+config PCI_SANDBOX_EP
+	bool "Sandbox PCIe endpoint controller"
+	depends on PCI_ENDPOINT
+	help
+	  Say Y here if you want to support the Sandbox PCIe controller in
+	  endpoint mode.
+	  The sandbox driver act as a dummy driver which stores and
+	  retrieves PCIe endpoint configuration as is.
+
 endmenu