[InstCombine] Add check of i1 types in select-to-zext/sext transformation

When doing select-to-zext/sext transformations, we should
not handle TrueVal and FalseVal of i1 type otherwise it
would result in zext/sext i1 to i1.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D93272