[unroll] Remove two dead variable assignments [nfc]

These variables are not out-params, and we immediately return after assigning them.  Thus, the assignments are dead and just confusing.

I believe these used to be out-params, but they're not any more.

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -982,8 +982,6 @@ bool llvm::computeUnrollCount(
   if (UnrollFactor) {
     UP.Count = *UnrollFactor;
     UseUpperBound = (FullUnrollMaxTripCount == FullUnrollTripCount);
-    TripCount = FullUnrollTripCount;
-    TripMultiple = UP.UpperBound ? 1 : TripMultiple;
     return ExplicitUnroll;
   } else {
     UP.Count = FullUnrollTripCount;