[SYCL][OpenMP] Implement thread-local storage restriction

Summary:
SYCL and OpenMP prohibits thread local storage in device code,
so this commit ensures that error is emitted for device code and not
emitted for host code when host target supports it.

Reviewers: jdoerfert, erichkeane, bader

Reviewed By: jdoerfert, erichkeane

Subscribers: guansong, riccibruno, ABataev, yaxunl, ebevhan, Anastasia, sstefan1, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D81641