Full suspension will not, by itself, prevent pinch flats. Since pinch flats are something that occur from the way the tire and tube move in regards to the rim, adding suspension won't change that. Now, adding suspension could move some of the pressure forward, depending on the pivots are arranged.
If you're riding at 40psi on a 2.10 tire, you should be fine on just dirt roads; however, if you hit a really nice square edged pot hot at that speed you're probably going to flat on either type of bike. Preventing pinch flats is usually more about tire pressure and deformation of the tire than anything else.