[Legalizer] Use correct ValueType of SELECT_CC node during Float promotion

Summary:
When legalizing the result of a SELECT_CC node by promoting the
floating-point type, use the promoted-to type rather than the original
type.

Fix PR40273.

Reviewers: efriedma, majnemer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D56566

llvm-svn: 350951