No, it is not wrong to ask for a calling.
When I joined the church, I was a YSA at a family ward. I was there for 3 years and never received a calling. I finally grew tired and asked for one, three months before I graduated and moved wards, they gave me one.
It is not good to always sit and wait around for a calling. Showing the motivation to ask for one is great, and it can also show the Bishop that you're really wanting to get involved with the members and the church as a whole.
Asking for a specific calling, now that is different. But asking for just A calling, that's perfectly fine.