SPECIAL: This musical salute to Prince, who died four years ago today, was taped January 28, when artists could still get together in the same venue, and people could still sit shoulder to shoulder and watch them. Renditions of Prince songs will be played by, among others, Morris Day and The Time, Sheila E., The Revolution, Usher, Mavis Staples, John Legend, Chris Martin, H.E.R., The Foo Fighters, Common, and Earth, Wind & Fire. The program is hosted by Maya Rudolph, who, in this special CBS