Test debug info in arg promotion with an actual promotion case, rather than a degenerate arg promotion that's actually DAE performed by ArgPromo

Also the debug location I had here was bogus, describing the location of
the call site as in the callee - and unnecessary, so just drop it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213803 91177308-0d34-0410-b5e6-96231b3b80d8