[InstSimplify] allow vector folds for (Pow2C << X) == NonPow2C

Existing pre-conditions seem to be correct:
https://rise4fun.com/Alive/lCLB

  Name: non-zero C1
  Pre: !isPowerOf2(C1) && isPowerOf2(C2) && C1 != 0
  %sub = shl i8 C2, %X
  %cmp = icmp eq i8 %sub, C1
  =>
  %cmp = false

  Name: one == C2
  Pre: !isPowerOf2(C1) && isPowerOf2(C2) && C2 == 1
  %sub = shl i8 C2, %X
  %cmp = icmp eq i8 %sub, C1
  =>
  %cmp = false

  Name: nuw
  Pre: !isPowerOf2(C1) && isPowerOf2(C2)
  %sub = shl nuw i8 C2, %X
  %cmp = icmp eq i8 %sub, C1
  =>
  %cmp = false

  Name: nsw
  Pre: !isPowerOf2(C1) && isPowerOf2(C2)
  %sub = shl nsw i8 C2, %X
  %cmp = icmp eq i8 %sub, C1
  =>
  %cmp = false