[FIX] stock_available_immediately: Restore current code

Due to merge mess, we need to restore current code this way

stock_available_immediately/__init__.py

@@ -3,4 +3,4 @@
 # Copyright 2019 Sergio Díaz <sergiodm.1989@gmail.com>
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
-from . import product_product
+from . import models

stock_available_immediately/models/__init__.py

@@ -0,0 +1,6 @@
+# Copyright 2014 Camptocamp, Akretion, Numérigraphe
+# Copyright 2016 Sodexis
+# Copyright 2019 Sergio Díaz <sergiodm.1989@gmail.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+
+from . import product_product

stock_available_immediately/models/product_product.py

@@ -6,8 +6,7 @@
 from odoo import api, models
 
 
-class Product(models.Model):
-    """Subtract incoming qty from immediately_usable_qty"""
+class ProductProduct(models.Model):
     _inherit = 'product.product'
 
     @api.multi