Explicitly don't let the asm printer use the clrb/w/l aliases for xor %reg, %reg.

It only didn't use it before because it seems InstAlias handling in the asm printer fails to count tied operands so it tried to find an xor with 2 operands instead of the 3 it wfails to count tied.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186900 91177308-0d34-0410-b5e6-96231b3b80d8