[SYCL][ESIMD][E2E] Disable loop.cpp because it's flaky (#16975)

Flaky fail.

Signed-off-by: Sarnie, Nick <[email protected]>

Author: sarnex

sycl/test-e2e/ESIMD/named_barriers/loop.cpp

@@ -5,7 +5,8 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-
+// UNSUPPORTED: arch-intel_gpu_pvc
+// UNSUPPORTED-TRACKER: https://github.com/intel/llvm/issues/16598
 // REQUIRES: arch-intel_gpu_pvc
 // RUN: %{build} -o %t.out
 // RUN: %{run} %t.out