[ValueTracking] Remove scalar only restriction from isKnownNonEqual. The...

[ValueTracking] Remove scalar only restriction from isKnownNonEqual. The computeKnownBits and isKnownNonZero calls this code relies on should work fine for vectors.

This will be used by another commit to remove some code from InstSimplify that is redundant for scalars, but was needed for vectors due to this issue.

llvm-svn: 304774