arm: qemu-ppce500: Add a devicetree file

This uses QEMU virt which creates its own devicetree.

Add an empty version of this file, so that we can at least build this
board when devicetrees are required.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/dts/Makefile b/arch/powerpc/dts/Makefile
index ceaa8ce..66d22ae 100644
--- a/arch/powerpc/dts/Makefile
+++ b/arch/powerpc/dts/Makefile
@@ -18,6 +18,7 @@
 dtb-$(CONFIG_TARGET_P3041DS) += p3041ds.dtb
 dtb-$(CONFIG_TARGET_P4080DS) += p4080ds.dtb
 dtb-$(CONFIG_TARGET_P5040DS) += p5040ds.dtb
+dtb-$(CONFIG_TARGET_QEMU_PPCE500) += qemu-ppce500.dtb
 dtb-$(CONFIG_TARGET_SOCRATES) += socrates.dtb
 dtb-$(CONFIG_TARGET_T1024RDB) += t1024rdb.dtb
 dtb-$(CONFIG_TARGET_T1042D4RDB) += t1042d4rdb.dtb