[X86] X86ScheduleBdVer2: use !listsplat operator to cleanup loadres calculation

[X86] X86ScheduleBdVer2: use !listsplat operator to cleanup loadres calculation

The problem is that one can't concatenate an empty list
(implied all-ones) with non-empty list here. The result
will be the non-empty list, and it won't match the length
of the ExePorts list.

The problems begin when LoadRes != 1 here,
which is the case in PdWriteResYMMPair,
and more importantly i think it will be the case for PdWriteResExPair.

llvm-svn: 358118