No, it does not.
The "Weapons and armor can be improved by X%" is only improving what you would already be able to make at Smithing level 100.
If you're trying to get your smithing to go over 100, you need "Fortify Smithing by X points."
According to the UESP, there are two items that will guarantee you find an item with the Fortify Smithing enchantment. Here's one. And here's two.
It's worth noting that the second one is a random radiant quest, so you may not get it on your first attempt.
I was mistaken, there is no "Fortify Smithing by X Points." The Fortify Smithing enchant only does the "Weapons and armor can be improved X% better."
However, even though your smithing skill won't go over 100, you will still get the benefits from the enchantment. For example, if you were to make a Legendary Dagger at 100 smithing, it might come out with, say, 14 damage. If you were to use your equipment to fortify your smithing and make the same dagger, you might get something to the effect of 20 damage, depending on what % of an increase there is from your gear/potions.