[DAGCombiner] Fix a couple mistakes from r324311 by really passing the...

[DAGCombiner] Fix a couple mistakes from r324311 by really passing the original load to ExtendSetCCUses.

We're passing the binary op that uses the load instead of the load.

Noticed by inspection. Not sure how to test this because this just prevents the introduction of an extend that will later be truncated and will probably be combined out.

llvm-svn: 324568