InstrProf: Don't emit counter increments in dead code

InstrProf: Don't emit counter increments in dead code

We were previously emitting counter increments even if we didn't have
an insertion point, which would result in a CallInst with no
parent. This leads to a crash, as in pr22166, if we try to do
GlobalDCE.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@225495 91177308-0d34-0410-b5e6-96231b3b80d8