So, is “The Huntsman: Winter’s War” a prequel or a sequel? In truth, it’s a bit of both, forming a wraparound tale which actually turns the original film into the dull middle chapter of a decent fantasy trilogy. “Winter’s War” takes us back to the beginnings of the Evil Queen Ravenna (Charlize Theron) and we see her power and kingdom grow while her little sister Freya (Emily Blunt) yearns for a…