[IndVars] Remove unreasonable checks in rewriteLoopExitValues

A piece of logic in rewriteLoopExitValues has a weird check on number of
users which allowed an unprofitable transform in case if an instruction has
more than 6 users.

Differential Revision: https://reviews.llvm.org/D51404
Reviewed By: etherzhhb


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342444 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed