[X86] Tidied up X86ISD instruction nodes. NFCI.

Tidied up comments, stripped trailing whitespace, split apart nodes that aren't related.

No change in ordering although there is definitely some scope for it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265263 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed