Implement Bluetooth settings factory reset (4/5)

Implemented the factory reset function to be used to reset all bluetooth
settings on device to factory default

Bug: 16161518
Change-Id: I69358db95582ddd0f2f640f76cf0931f797d369b

include/hardware/bluetooth.h

@@ -542,6 +542,12 @@ typedef struct {
      * Function is synchronous and |fd| is owned by caller.
      */
     void (*dump)(int fd);
+
+    /**
+     * Clear /data/misc/bt_config.conf and erase all stored connections
+     */
+    int (*config_clear)(void);
+
 } bt_interface_t;
 
 /** TODO: Need to add APIs for Service Discovery, Service authorization and