Fix initializing TypeOfTypeLoc

This fixes a crash in the RecursiveASTVisitor on such code
 __typeof__(struct F*) var[invalid];

The UnderlyingTInfo of a TypeOfTypeLoc was left uninitialized when
created from ASTContext::getTrivialTypeSourceInfo
This lead to a crash in RecursiveASTVisitor when trying to access it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220562 91177308-0d34-0410-b5e6-96231b3b80d8