Revert "[GlobalISel] track predecessor mapping during switch lowering."

This reverts commit r291973.

The test fails in a Release build with LLVM_BUILD_GLOBAL_ISEL enabled.
AFAICT, llc segfaults. I'll add a few more details to the original
commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292061 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed