Install python3-edgetpu on excelsior

Change-Id: Ie35f32cd0b8e591b03d64f4104fdc654eadaf245
diff --git a/rootfs.mk b/rootfs.mk
index 9dab04c..fc0ef82 100644
--- a/rootfs.mk
+++ b/rootfs.mk
@@ -17,6 +17,7 @@
     excelsior-wlan \
     linux-image-4.4.22-mtk \
     lk-bootloader \
+    python3-edgetpu \
     trustzone
 
 BSP_GUI_PACKAGES :=