[SchedModel] Use std::move to replace a vector instead of vector::swap

[SchedModel] Use std::move to replace a vector instead of vector::swap

We don't really care about the old vector value so we don't care to swap it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328440 91177308-0d34-0410-b5e6-96231b3b80d8