[PR40778][Sema] Adjust addr space of operands in builtin operators.

Adjust address space for references and pointer operands of builtin operators.

Currently this change only fixes addr space in assignment (= and |=) operator,
that is needed for the test case reported in the bug. Wider support for all
other operations will follow.

Differential Revision: https://reviews.llvm.org/D58719

llvm-svn: 355608