InstCombine: Optimize x/INT_MIN to x==INT_MIN

The result of x/INT_MIN is either 0 or 1, we can just use an icmp
instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212167 91177308-0d34-0410-b5e6-96231b3b80d8