[LegalizeDAG] Fix legalization of SETCC

Summary:
Currently when expanding a SETCC node into a SELECT_CC, LLVM uses
an incorrect type for determining BooleanContent of the result. This
patch fixes the issue.

Fixes PR36079.

Reviewers: rogfer01, javed.absar, efriedma

Reviewed By: efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D43282

llvm-svn: 325325