added A/B partition update

resources/scripts/ab_active

@@ -0,0 +1,11 @@
+ #!/bin/bash
+set -e
+
+# get current partition index
+current_idx=$(rdev | sed 's#/dev/mmcblk0p\([^ ]*\).*#\1#')
+
+if [ $current_idx -eq 2 ]; then
+    echo "Active partition: A"
+else
+    echo "Active partition: B"
+fi