dm: sandbox: pci: Add PCI support for sandbox

Add the required header information, device tree nodes and I/O accessor
functions to support PCI on sandbox. All devices are emulated by drivers
which can be added as required for testing or development.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/lib/Makefile b/arch/sandbox/lib/Makefile
index 4c1a38d..75b135c 100644
--- a/arch/sandbox/lib/Makefile
+++ b/arch/sandbox/lib/Makefile
@@ -7,5 +7,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-
 obj-y	+= interrupts.o
+obj-$(CONFIG_PCI)	+= pci_io.o