Your confusing Special Relativity with General Relativity. The whole mass-energy thing (aka e = mc2), and indeed the speed of light restriction is described under Special Relativity, which governs the motion of objects
through space. Comsological expansion (aka the expansion
of space) is derived from the Freidman-Robertson-Walker metric using General Relativity and there is no such restriction. This is probably the most misunderstood aspect of the whole big bang/expanding universe model. Think of it as one laying down the rules
within the bubble, the other laying down the rules
of the bubble.
Within any local frame of reference, the speed of light will always be constant (Special Relativity), even though to a distant observer an object might be receeding superluminally (General Relativity). But even the distant observer will still only see the light reaching them at the speed of light, just cosmologically (not Doppler) redshifted.
This stuff can really do your head in
.