Use unique_ptr to simplify deletion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222929 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a few memory leaks in CodeGenRegBank.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222930 91177308-0d34-0410-b5e6-96231b3b80d8