[ADT] Add missing const_iterator DenseSet::find() const

Summary: Probably overlooked.

Reviewers: eugenis, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D24689

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283377 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed