In Minnesota, the policemen would be guilty of murder in the first degree if they "caused the death of a human being with premeditation and with intent to effect the death of the person or of another."
They would be guilty of murder in the second degree if they "caused the death of a human being with intent to effect the death of that person or another, but without premeditation."
They would be guilty of murder in the third degree if they "without intent to effect the death of any person, caused the death of another by perpetrating an act eminently dangerous to others and evincing a depraved mind, without regard for human life."
I don't see how a policeman, in the course of his duties, applying a restraint technique valid in the state of Minnesota, could successfully be prosecuted under any of those charges.
On the other hand, police departments across the US have made clear that any policeman doing what was shown in the video would not retain his job -- because, at the very least, (1) a very dangerous form of restraint was used, and (2) the police involved did not adequately monitor Floyd's breathing.