[DAG] Don't map a TableId to itself in the ReplacedValues map

Summary:
Found some regressions (infinite loop in DAGTypeLegalizer::RemapId)
after r334880. This patch makes sure that we do map a TableId to
itself.

Reviewers: niravd

Reviewed By: niravd

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D48364

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335141 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed