[CodeGen] Default CTTZ_ZERO_UNDEF/CTLZ_ZERO_UNDEF to Expand in TargetLoweringBase. This is what the majority of the targets want and removes a bunch of code. Set it to Legal explicitly in the few cases where that's the desired behavior.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267853 91177308-0d34-0410-b5e6-96231b3b80d8
15 files changed