[LoopAccesses] Properly print whether memchecks are needed

[LoopAccesses] Properly print whether memchecks are needed

Fix oversight in -analyze output.  PtrRtCheck contains the pointers that
need to be checked against each other and not whether memchecks are
necessary.

For instance in the testcase PtrRtCheck has four elements but all
no-alias so no checking is necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234833 91177308-0d34-0410-b5e6-96231b3b80d8