[Hexagon] Set ctlz_zero_undef/cttz_zero_undef to Expand so LegalizeDAG will convert them to ctlz/cttz. Remove the now unneccessary isel patterns. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267266 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed