[OPENMP] Fixed codegen for __real/__imag expressions in atomic

[OPENMP] Fixed codegen for __real/__imag expressions in atomic
constructs.

For __real/__imag unary expressions clang emits lvalue with the
associated type from the original complex expression, but not the
underlying builtin integer or float type. This causes crash in codegen
for atomic constructs, if __real/__imag expression are used in atomic
  constructs.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@286129 91177308-0d34-0410-b5e6-96231b3b80d8