edgetpudemo: Add in the edgetpudemo package

Change-Id: I00fc3f33eb0288e2ddaedc2014127a47221b4f8e
diff --git a/rootfs.mk b/rootfs.mk
index 93b8299..f54236b 100644
--- a/rootfs.mk
+++ b/rootfs.mk
@@ -25,5 +25,6 @@
 	linux-image-4.9.51-imx \
 	python3-edgetpu \
 	python3-edgetpuvision \
+	edgetpudemo \
 	uboot-imx \
 	usb-gadget