[CodeGen] Fix incorrectly detected reduction bug in ComplexDeinterleaving pass

Using ACLE intrinsics, it is possible to create a loop that the
deinterleaving pass incorrectly classified as a reduction loop.
For example, for fixed-width vectors the loop was like below:

vector.body:
  %a = phi <4 x float> [ %init.a, %entry ], [ %updated.a, %vector.body ]
  %b = phi <4 x float> [ %init.b, %entry ], [ %updated.b, %vector.body ]
  ...
; Does not depend on %a or %b:
  %updated.a = ...
  %updated.b = ...

Differential Revision: https://reviews.llvm.org/D154598