bluetooth: hids: Fix bt_hogp_rep_unsubscribe issue

The bt_hogp_rep_unsubscribe did not reset the rep->notify_cb,
while bt_hogp_rep_subscribe returned an error if
notify_cb was not null. Thus, it would be impossible
to subscribe again to the report notification after
unsubscribing.

This commit fixes this.

Signed-off-by: Artur Hadasz <artur.hadasz@nordicsemi.no>

Author: ahasztag

subsys/bluetooth/services/hogp.c

@@ -1077,10 +1077,19 @@ int bt_hogp_rep_subscribe(struct bt_hogp *hogp,
 int bt_hogp_rep_unsubscribe(struct bt_hogp *hogp,
 			    struct bt_hogp_rep_info *rep)
 {
+	int ret;
+
 	if (!hogp || !rep) {
 		return -EINVAL;
 	}
-	return bt_gatt_unsubscribe(hogp->conn, &rep->notify_params);
+
+	ret = bt_gatt_unsubscribe(hogp->conn, &rep->notify_params);
+
+	if (!ret) {
+		rep->notify_cb = NULL;
+	}
+
+	return ret;
 }
 
 /**