Revert "[Sema] Make canPassInRegisters return true if the CXXRecordDecl passed"

This reverts commit r350920 as it is not clear whether we should force a
class to be returned in registers when copy and move constructors are
both deleted.

For more background, see the following discussion:
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20190128/259907.html

llvm-svn: 352822