[SelectionDAG] Tidyup UDIV computeKnownBits implementation

No need to clear KnownOne2/KnownZero2 bits as the next call to computeKnownBits will overwrite them anyway

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285398 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed