Mark a couple of the X86 target classes as final. Allows the compiler to de-virtualize some internal calls.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205165 91177308-0d34-0410-b5e6-96231b3b80d8
[C++11] Mark more classes in the X86 target as 'final'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205166 91177308-0d34-0410-b5e6-96231b3b80d8