[DAGCombiner] Avoid creating truncate nodes in (zext (and (load)))->(and...

[DAGCombiner] Avoid creating truncate nodes in (zext (and (load)))->(and (zextload)) fold until we know for sure we're going to need it. NFCI

The truncate is only needed if the load has additional users. It used to get passed to extendSetCCUses so was created early, but that's no longer the case.

llvm-svn: 324562