Fix wrong iterator type

Fix wrong iterator type

ELFEntityIterator does not implement RandomAccessIterator. It does
not even implement BidirectionalIterator.

This patch fixes LLD build issue when compiled with MSVC2013 with
debug: MSVC's find_if checks if the start iterator is before the end
iterator in the sense of operator< if it declares implementing
RandomAccessIterator. If a class does not have operator<, it fails
to compile.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206825 91177308-0d34-0410-b5e6-96231b3b80d8