dm: sandbox: Add a simple PCI driver

Add a driver which can access emulations of devices and make them available
in sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index db82786..9e2e5f9 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -7,6 +7,7 @@
 
 ifneq ($(CONFIG_DM_PCI),)
 obj-$(CONFIG_PCI) += pci-uclass.o pci_compat.o
+obj-$(CONFIG_PCI_SANDBOX) += pci_sandbox.o
 else
 obj-$(CONFIG_PCI) += pci.o
 endif