Don't allow the automatically updated MI flags to be set directly.

Don't allow the automatically updated MI flags to be set directly.

The bundle-related MI flags need to be kept in sync with the neighboring
instructions. Don't allow the bulk flag-setting setFlags() function to
change them.

Also don't copy MI flags when cloning an instruction. The clone's bundle
flags will be set when it is explicitly inserted into a bundle.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170459 91177308-0d34-0410-b5e6-96231b3b80d8