[InstCombine] matchThreeWayIntCompare(): commutativity awareness

Summary:
`matchThreeWayIntCompare()` looks for
```
   select i1 (a == b),
          i32 Equal,
          i32 (select i1 (a < b), i32 Less, i32 Greater)
```
but both of these selects/compares can be in it's commuted form,
so out of 8 variants, only the two most basic ones is handled.
This fixes regression being introduced in D66232.

Reviewers: spatel, nikic, efriedma, xbolva00

Reviewed By: spatel

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66607

llvm-svn: 369841