Update RuntimeDyldELF::findOPDEntrySection the new relocation iterators.

This was missing from r182908. I didn't noticed it at the time because the MCJIT tests were
disabled when building with cmake on ppc64 (which I fixed in r183143).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183147 91177308-0d34-0410-b5e6-96231b3b80d8