[lldb] Unwrap the type when dereferencing the value

The value type can be a typedef of a reference (e.g. `typedef int& myint`).
In this case `GetQualType(type)` will return `clang::Typedef`, which cannot
be casted to `clang::ReferenceType`.

Fix a regression introduced in https://reviews.llvm.org/D103532.

Reviewed By: teemperor

Differential Revision: https://reviews.llvm.org/D113673