[X86] Don't lie about legality to TLI's demanded bits.

Like r309323, X86 had a typo where it passed the wrong flags to TLO.

Found by inspection; I haven't been able to tickle this into having
observable behavior.  I don't think it does, given that X86 doesn't have
custom demanded bits logic, and the generic logic doesn't have a lot of
exposure to illegal constructs.

llvm-svn: 309325