Depending on the severity of the break and where the break occurred he may only be out 4-6 weeks or so, if surgery isn't required. The Fibula is the non weight-bearing bone in the leg. Keep in mind, Travis Henry played with a hairline fracture of his fibula last year.
By no means am I comparing the two injuries, as I believe Smith's to be the more serious injury. But, if no surgery is required and the break isn't very close to the ankle, I think Smith could be back before the mid-point of the season, if not a little earlier. The Panther's have an early BYE so that's one extra week of healing that Smith owners wouldn't have had him for anyway.
Here's hoping for a speedy recovery.