Config utils improvement

Added a function to free resources allocated by config node tree.

Change-Id: I2ee8ae642899ec4501fa6e490c5be7efaa2d738e
diff --git a/include/cutils/config_utils.h b/include/cutils/config_utils.h
index f3fb370..2dea6f1 100644
--- a/include/cutils/config_utils.h
+++ b/include/cutils/config_utils.h
@@ -54,6 +54,9 @@
 /* add a named child to a config node (or modify it if it already exists) */
 void config_set(cnode *root, const char *name, const char *value);
 
+/* free a config node tree */
+void config_free(cnode *root);
+
 #ifdef __cplusplus
 }
 #endif