small oil potion buff file

In the mod there is a new item, named potion_oil_small, it use the same slots as the normal oil, but ingame the model it's smaller, and so it provides a lower amount of oil. In the normal version, it provides a exaggeratedly of fuel for the lantern, and so I decided to give it a buff, providing the double amount of fuel in comparison of before, but still lower than a normal oil potion. A these are findable only on alternative areas, it makes more sense to give them a buff.