backup: fix backup on 7.0 :)

Change-Id: I5eea8361020104ee95a3fd56107a8a39f180dc85
diff --git a/prebuilt/bin/backuptool.sh b/prebuilt/bin/backuptool.sh
index ad957e7..799011d 100755
--- a/prebuilt/bin/backuptool.sh
+++ b/prebuilt/bin/backuptool.sh
@@ -5,7 +5,7 @@
 
 export C=/tmp/backupdir
 export S=/system
-export V=6.0
+export V=7.0
 
 # Preserve /system/addon.d in /tmp/addon.d
 preserve_addon_d() {