[NFC][SYCL] Enable temporarily disabled LIT tests (#2244)

- Enable LIT test which were disabled to unblock submission of PR#2148
- Disable generic-shuffle.cpp due to bug in OpenCL CPU RT

Author: vladimirlaz

sycl/test/hier_par/hier_par_wgscope_O0.cpp

@@ -13,7 +13,7 @@
 // RUN: %GPU_RUN_PLACEHOLDER %t.out
 // RUN: %ACC_RUN_PLACEHOLDER %t.out
 
-// UNSUPPORTED: accelerator || (system-windows && cpu)
+// XFAIL: system-windows && cpu
 
 // This test checks correctness of hierarchical kernel execution when there is
 // code and data in the work group scope, and when the test is compiled with

sycl/test/sub_group/generic-shuffle.cpp

@@ -1,5 +1,6 @@
 // UNSUPPORTED: cuda || cpu
 // CUDA compilation and runtime do not yet support sub-groups.
+// #2245 failed on OpenCL CPU (2020.10.7.0.15) with avx2 instruction set
 //
 // RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %s -o %t.out
 // RUN: env SYCL_DEVICE_TYPE=HOST %t.out