Leather may be an especially difficult material to remove smoke smell becaue its porous organic fibers will absorb and hold those stains & odors literally forever!
You can try using a good quality leather cleaning product, then a leather conditioner, let it air out well and maybe you'll find it somewhat better. I doubt you'll ever get the smell out. If it sit in the heat or locked up the a stored RV...the smell may still come out again. In time...you will either get used to it or get rid of it.
If it were me...I'd give it to another smoker and go buy youself a new chair!
I'd not spray it with Febreze because it could damage the material. Febreze works best on cloth fabric not leather.