[X86] LowerBUILD_VECTOR - fold build_vector(undef,freeze(undef),zero) -> zero vector

426db6b4 added the build_vector(undef,freeze(undef)) -> freeze(undef) fold, but failed to account for cases where the scalar freeze(undef) had multiple uses, in those cases we can only only safely fold to a zero vector

https://alive2.llvm.org/ce/z/87jG8K