Revert r309415: "[LVI] Constant-propagate a zero extension of the switch condition value through case edges"

This causes assertion failures in (a somewhat old version of) SpiderMonkey.
I have already forwarded reproduction instructions to the patch author.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309659 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed